Infrared Spectroscopy | A Level Chemistry<\/title>\n<link href=\"https:\/\/fonts.googleapis.com\/css2?family=Poppins:wght@300;400;500;600&display=swap\" rel=\"stylesheet\">\n<style>\nbody {\n margin: 0;\n padding: 40px 0;\n background: #ffffff;\n font-family: Poppins, Arial, sans-serif;\n}\n<\/style>\n<p><\/head><br \/>\n<body><br \/>\n<\/p>\n<style>\n.ols-hero-section-blog-001 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-hero-section-blog-001 {\n max-width: 1100px;\n margin: 0 auto 56px auto;\n padding: 0 16px;\n}\n.ols-hero-section-blog-001 .ols-hero-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 26px;\n overflow: hidden;\n box-shadow: 0 10px 28px rgba(0,0,0,0.08);\n}\n.ols-hero-section-blog-001 .ols-hero-image img {\n width: 100%;\n height: 420px;\n object-fit: cover;\n display: block;\n}\n.ols-hero-section-blog-001 .ols-hero-content {\n padding: 36px 40px 40px 40px;\n}\n.ols-hero-section-blog-001 .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin-bottom: 18px;\n}\n.ols-hero-section-blog-001 .ols-title {\n font-size: 40px;\n font-weight: 600;\n line-height: 1.15;\n color: #1C244B;\n margin: 0 0 10px 0;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-hero-section-blog-001 .ols-line {\n width: 90px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 22px 0;\n}\n.ols-hero-section-blog-001 .ols-excerpt {\n font-size: 22px;\n font-weight: 300;\n line-height: 1.75;\n color: #374151;\n}\n@media (max-width: 900px) {\n .ols-hero-section-blog-001 .ols-hero-image img { height: 320px; }\n .ols-hero-section-blog-001 .ols-title { font-size: 30px; }\n .ols-hero-section-blog-001 .ols-excerpt { font-size: 18px; }\n .ols-hero-section-blog-001 .ols-hero-content { padding: 26px 24px; }\n}\n@media (max-width: 480px) {\n .ols-hero-section-blog-001 .ols-title { font-size: 24px; }\n .ols-hero-section-blog-001 .ols-excerpt { font-size: 16px; }\n}\n<\/style>\n<p> <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/03\/infrared-spectroscopy-greenhouse-effect-illustration.png\"\n alt=\"Infrared spectroscopy used to study molecular vibrations and greenhouse gases like carbon dioxide and methane\"><br \/>\n A Level Chemistry<\/p>\n<h1>Infrared Spectroscopy<\/h1>\n<p>\n Infrared spectroscopy is one of the most powerful tools in modern chemistry, used to identify bonds, study molecular vibrations and even monitor greenhouse gases like CO\u2082 and methane. Discover how bond stretching, bending and dipole moments allow molecules to absorb infrared radiation and why this technique is essential for A-Level Chemistry.\n <\/p>\n<p><\/p>\n<style>\n.ols-info-section-ir-001 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-001 {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-001 .ols-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-001 .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-001 .ols-title {\n margin: 0 0 8px 0;\n font-size: 34px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-001 .ols-line {\n width: 80px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-001 .ols-top-grid {\n display: grid;\n grid-template-columns: 1fr 1fr;\n gap: 26px;\n align-items: start;\n margin-top: 26px;\n}\n.ols-info-section-ir-001 .ols-bottom-grid {\n display: grid;\n grid-template-columns: 1fr;\n margin-top: 26px;\n}\n.ols-info-section-ir-001 .ols-text-card,\n.ols-info-section-ir-001 .ols-image-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-001 .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0 0 18px 0;\n}\n.ols-info-section-ir-001 .ols-body:last-child { margin-bottom: 0; }\n.ols-info-section-ir-001 .ols-image-card { padding: 20px; }\n.ols-info-section-ir-001 .ols-image-card img {\n width: 100%;\n display: block;\n border-radius: 14px;\n}\n.ols-info-section-ir-001 .ols-image-caption {\n margin-top: 14px;\n color: #1C244B;\n font-size: 14px;\n font-weight: 500;\n line-height: 1.4;\n text-align: center;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-001 .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-001 .ols-title { font-size: 26px; }\n .ols-info-section-ir-001 .ols-body { font-size: 16px; }\n .ols-info-section-ir-001 .ols-top-grid { grid-template-columns: 1fr; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-001 .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-001 .ols-title { font-size: 22px; }\n .ols-info-section-ir-001 .ols-body { font-size: 15px; }\n .ols-info-section-ir-001 .ols-text-card,\n .ols-info-section-ir-001 .ols-image-card { padding: 18px 16px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h2>Greenhouse Gases<\/h2>\n<p>\n Climate change affects the global environment and is strongly influenced by human activity. To limit atmospheric pollution, countries have created international agreements such as the Kyoto Protocol. These agreements aim to reduce emissions of major greenhouse gases including CO\u2082, methane (CH\u2084), nitrous oxide (N\u2082O), and ozone (O\u2083). Monitoring these gases is important for understanding their environmental impact.\n <\/p>\n<p>\n Measurements show that carbon dioxide levels in the atmosphere have increased significantly over the past 50 years. Data from ice cores indicate that before industrialisation, atmospheric CO\u2082 was about 278 ppm. Between 1000 and 1800, it varied by only about 7 ppm, showing that natural levels were relatively stable.\n <\/p>\n<p> <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/03\/infrared-spectroscopy-greenhouse-gases-diagram.png\"\n alt=\"Infrared spectroscopy diagram showing greenhouse gases including carbon dioxide, methane, nitrous oxide and ozone\"><br \/>\n Greenhouse gases absorb infrared radiation at specific wavelengths, allowing their concentrations to be monitored.<\/p>\n<p>\n However, between 1958 and 2004, atmospheric CO\u2082 increased from around 315 ppm to 378 ppm. Compared with the pre-industrial level of 278 ppm, this represents an increase of about 100 ppm, which is approximately 36% higher. This rise is largely linked to human activities such as burning fossil fuels and deforestation.\n <\/p>\n<p>\n Atmospheric gas concentrations are commonly measured using infrared spectroscopy, because greenhouse gases absorb infrared radiation at specific wavelengths. This allows scientists to detect and quantify the gases present in the atmosphere.\n <\/p>\n<p><\/p>\n<style>\n.ols-info-section-ir-002 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-002 {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-002 .ols-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-002 .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-002 .ols-title {\n margin: 0 0 8px 0;\n font-size: 34px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-002 .ols-line {\n width: 80px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-002 .ols-top-grid {\n display: grid;\n grid-template-columns: 1fr 1fr;\n gap: 26px;\n align-items: start;\n margin-top: 26px;\n}\n.ols-info-section-ir-002 .ols-bottom-grid {\n display: grid;\n grid-template-columns: 1fr;\n margin-top: 26px;\n}\n.ols-info-section-ir-002 .ols-text-card,\n.ols-info-section-ir-002 .ols-image-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-002 .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0 0 18px 0;\n}\n.ols-info-section-ir-002 .ols-body:last-child { margin-bottom: 0; }\n.ols-info-section-ir-002 .ols-body strong {\n font-weight: 600;\n color: #1C244B;\n}\n.ols-info-section-ir-002 .ols-body a {\n color: #1C244B;\n text-decoration: underline;\n text-underline-offset: 3px;\n text-decoration-thickness: 1px;\n}\n.ols-info-section-ir-002 .ols-image-card { padding: 20px; }\n.ols-info-section-ir-002 .ols-image-card img {\n width: 100%;\n display: block;\n border-radius: 14px;\n}\n.ols-info-section-ir-002 .ols-image-caption {\n margin-top: 14px;\n color: #1C244B;\n font-size: 14px;\n font-weight: 500;\n line-height: 1.4;\n text-align: center;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-002 .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-002 .ols-title { font-size: 26px; }\n .ols-info-section-ir-002 .ols-body { font-size: 16px; }\n .ols-info-section-ir-002 .ols-top-grid { grid-template-columns: 1fr; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-002 .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-002 .ols-title { font-size: 22px; }\n .ols-info-section-ir-002 .ols-body { font-size: 15px; }\n .ols-info-section-ir-002 .ols-text-card,\n .ols-info-section-ir-002 .ols-image-card { padding: 18px 16px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h2>How Molecular Bond Vibrations Produce Infrared Absorption<\/h2>\n<p>\n Even when molecules are part of a solid structure, the atoms within them are not completely still. The bonds between atoms constantly vibrate, stretching and compressing while the molecule also bends slightly. Each of these vibrations happens at a specific frequency, which depends on the atoms involved in the bond and how they are connected.\n <\/p>\n<p>\n All molecules can absorb energy. When a molecule absorbs energy that matches the vibrational energy of one of its bonds, the vibration becomes stronger. In other words, the amplitude of the vibration increases and the bond enters what is called an excited state.\n <\/p>\n<p> <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/03\/infrared-spectroscopy-dipole-moment-diagram.png\"\n alt=\"Infrared spectroscopy diagram showing molecular bond vibrations and changing dipole moment\"><br \/>\n Infrared absorption occurs when a bond vibration causes a change in dipole moment.<\/p>\n<p>\n After a short time, the molecule returns to its <strong>ground state<\/strong> and releases the absorbed energy. This energy can be detected, and because each bond vibrates at its own characteristic frequency, the detected energy provides information about the types of bonds present in the molecule. These frequencies lie in the <strong>infrared region of the electromagnetic spectrum<\/strong>, which is why this technique is called <strong>infrared (IR) spectroscopy<\/strong>.\n <\/p>\n<p>\n Like other analytical techniques such as <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/how-x-rays-reveal-the-structure-of-metal-crystals\/\" target=\"_blank\" rel=\"noopener\">X-ray diffraction<\/a>, infrared spectroscopy gives chemists a powerful way to investigate molecules and the bonds that hold them together.\n <\/p>\n<p>\n However, not every bond in a molecule will absorb infrared radiation. For absorption to occur, the vibration must cause a <strong>change in the dipole moment<\/strong> of the bond.\n <\/p>\n<p>\n A <strong>dipole moment<\/strong> exists when there is a separation of charge in a bond. It is defined as the <strong>magnitude of the charge multiplied by the distance between the charges<\/strong>. Many bonds have a dipole moment because the atoms involved have <strong>different electronegativities<\/strong>, meaning the electrons are shared unevenly. When these bonds vibrate, the dipole moment changes, allowing the bond to absorb infrared radiation.\n <\/p>\n<p>\n For a more detailed look at the underlying theory, you can explore this overview of <a href=\"https:\/\/chem.libretexts.org\/Courses\/Providence_College\/Organic_Chemistry_I\/05%3A_Analytical_Methods_for_Structure_Elucidation\/5.04%3A_Infrared_Spectroscopy\" target=\"_blank\" rel=\"noopener\">infrared spectroscopy from Chemistry LibreTexts<\/a>, which covers the same concepts at undergraduate level.\n <\/p>\n<p><\/p>\n<style>\n.ols-info-section-ir-003 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-003 {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-003 .ols-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-003 .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-003 .ols-title {\n margin: 0 0 8px 0;\n font-size: 30px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-003 .ols-line {\n width: 70px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-003 .ols-grid {\n display: grid;\n grid-template-columns: 1fr 1fr;\n gap: 26px;\n align-items: start;\n margin-top: 26px;\n}\n.ols-info-section-ir-003 .ols-text-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-003 .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0 0 18px 0;\n}\n.ols-info-section-ir-003 .ols-body:last-child { margin-bottom: 0; }\n.ols-info-section-ir-003 .ols-body strong {\n font-weight: 600;\n color: #1C244B;\n}\n.ols-info-section-ir-003 ul {\n margin: 10px 0 18px 18px;\n color: #374151;\n font-size: 18px;\n font-weight: 300;\n line-height: 1.8;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-003 .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-003 .ols-title { font-size: 24px; }\n .ols-info-section-ir-003 .ols-body,\n .ols-info-section-ir-003 ul { font-size: 16px; }\n .ols-info-section-ir-003 .ols-grid { grid-template-columns: 1fr; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-003 .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-003 .ols-title { font-size: 20px; }\n .ols-info-section-ir-003 .ols-body,\n .ols-info-section-ir-003 ul { font-size: 15px; }\n .ols-info-section-ir-003 .ols-text-card { padding: 18px 16px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h3>When Bonds Absorb Infrared Radiation<\/h3>\n<p>\n Not all molecules absorb infrared radiation. In symmetrical molecules, there may be no overall dipole moment. This can happen if there is no separation of charge, such as in diatomic molecules made from the same element, or when the dipole moments of individual bonds cancel each other out. When this occurs, infrared radiation is not absorbed.\n <\/p>\n<p>\n However, when bonds stretch or bend, the dipole moment of the molecule can change. If this change occurs during the vibration, the bond is able to absorb infrared radiation.\n <\/p>\n<p>\n Some bonds produce strong infrared absorptions, particularly polar bonds such as C\u2013O, C=O and O\u2013H. These bonds have significant differences in electronegativity between the atoms, so their dipole moments change noticeably during vibration. In contrast, non-polar bonds such as C\u2013C and C=C usually produce much weaker absorptions.\n <\/p>\n<p>\n There are two main types of molecular vibration:\n <\/p>\n<ul>\n<li>Stretching vibrations, where the bond length increases and decreases.<\/li>\n<li>Bending vibrations, where the bond angle changes.<\/li>\n<\/ul>\n<p>\n Bending vibrations require less energy than stretching vibrations, so they occur at lower energy and longer wavelengths in the infrared region.\n <\/p>\n<p>\n In planar molecules, such as sulphur dioxide (SO\u2082) and carbon dioxide (CO\u2082), infrared radiation can be absorbed through either bond stretching or bond bending vibrations.\n <\/p>\n<p><\/p>\n<style>\n.ols-cta-section-ir-001 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-cta-section-ir-001 {\n max-width: 1100px;\n margin: 0 auto 60px auto;\n padding: 0 16px;\n}\n.ols-cta-section-ir-001 .ols-cta-card {\n display: grid;\n grid-template-columns: 1.2fr 1fr;\n gap: 0;\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 26px;\n overflow: hidden;\n box-shadow: 0 12px 28px rgba(0,0,0,0.08);\n}\n.ols-cta-section-ir-001 .ols-cta-image img {\n width: 100%;\n height: 100%;\n object-fit: cover;\n display: block;\n}\n.ols-cta-section-ir-001 .ols-cta-content {\n padding: 40px 44px;\n display: flex;\n flex-direction: column;\n justify-content: center;\n}\n.ols-cta-section-ir-001 .ols-pill {\n display: inline-block;\n background: #6B1A1A;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin-bottom: 18px;\n}\n.ols-cta-section-ir-001 .ols-title {\n font-size: 34px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n margin: 0 0 12px 0;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-cta-section-ir-001 .ols-line {\n width: 80px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin-bottom: 20px;\n}\n.ols-cta-section-ir-001 .ols-desc {\n font-size: 20px;\n font-weight: 300;\n line-height: 1.8;\n color: #374151;\n margin-bottom: 28px;\n}\n.ols-cta-section-ir-001 .ols-btn {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 15px;\n font-weight: 500;\n padding: 12px 22px;\n border-radius: 999px;\n text-decoration: none;\n width: fit-content;\n transition: all 0.25s ease;\n}\n.ols-cta-section-ir-001 .ols-btn:hover {\n background: #000;\n transform: translateY(-2px);\n}\n@media (max-width: 900px) {\n .ols-cta-section-ir-001 .ols-cta-card { grid-template-columns: 1fr; }\n .ols-cta-section-ir-001 .ols-cta-image img { height: 260px; }\n .ols-cta-section-ir-001 .ols-cta-content { padding: 28px 24px; }\n .ols-cta-section-ir-001 .ols-title { font-size: 26px; }\n .ols-cta-section-ir-001 .ols-desc { font-size: 17px; }\n}\n@media (max-width: 480px) {\n .ols-cta-section-ir-001 .ols-title { font-size: 22px; }\n .ols-cta-section-ir-001 .ols-desc { font-size: 15px; }\n}\n<\/style>\n<p> <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/04\/edexcel-international-a-level-chemistry-topic-2-atomic-structure-periodic-table-course-banner.jpg\"\n alt=\"A-Level Chemistry course on covalent bonding, molecular shapes and symmetry of molecules\"><br \/>\n A Level Chemistry Course<\/p>\n<h3>Master Molecular Shapes & Covalent Bonding<\/h3>\n<p>\n Take your understanding further with our complete A-Level Chemistry course on covalent bonding, molecular geometry and the symmetry of molecules.\n <\/p>\n<p> <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/covalent-bonding-shapes-of-molecules-edexcel-t3b-c\/\"><br \/>\n Explore the Course<br \/>\n <\/a><br \/>\n<\/p>\n<style>\n.ols-info-section-ir-005-a * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-005-a {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-005-a .ols-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-005-a .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-005-a .ols-title {\n margin: 0 0 8px 0;\n font-size: 30px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-005-a .ols-line {\n width: 70px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-005-a .ols-stack {\n display: flex;\n flex-direction: column;\n gap: 22px;\n margin-top: 26px;\n}\n.ols-info-section-ir-005-a .ols-text-card,\n.ols-info-section-ir-005-a .ols-image-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-005-a .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0;\n}\n.ols-info-section-ir-005-a .ols-image-card img {\n width: 100%;\n display: block;\n border-radius: 14px;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-005-a .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-005-a .ols-title { font-size: 24px; }\n .ols-info-section-ir-005-a .ols-body { font-size: 16px; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-005-a .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-005-a .ols-title { font-size: 20px; }\n .ols-info-section-ir-005-a .ols-body { font-size: 15px; }\n .ols-info-section-ir-005-a .ols-text-card,\n .ols-info-section-ir-005-a .ols-image-card { padding: 18px 16px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h3>Sulphur Dioxide (SO\u2082)<\/h3>\n<p>\n Each type of molecular vibration can cause a change in the dipole moment of the molecule. When this happens, the molecule is able to absorb infrared radiation at the frequency corresponding to that vibration. Because different vibrational motions occur at different energies, each one produces a separate absorption in the infrared spectrum.\n <\/p>\n<p>\n As a result, a molecule can show multiple absorption peaks, with each peak representing a specific type of bond vibration. For example, sulphur dioxide (SO\u2082) has three possible vibrational motions. Since each of these vibrations changes the dipole moment, all three absorb infrared radiation.\n <\/p>\n<p>\n This means the infrared spectrum of sulphur dioxide shows three distinct absorption peaks, each corresponding to one of its vibrational modes.\n <\/p>\n<p> <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/03\/infraredspectrumso2.png\"\n alt=\"Infrared spectrum of sulphur dioxide showing three absorption peaks corresponding to different vibrational modes\"><br \/>\n<\/p>\n<style>\n.ols-info-section-ir-004 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-004 {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-004 .ols-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-004 .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-radius: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-004 .ols-title {\n margin: 0 0 8px 0;\n font-size: 30px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-004 .ols-line {\n width: 70px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-004 .ols-text-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-004 .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0;\n}\n.ols-info-section-ir-004 .ols-viewer-wrap {\n margin-top: 28px;\n border-radius: 18px;\n overflow: hidden;\n border: 1px solid #e5e7eb;\n}\n.ols-info-section-ir-004 .ols-viewer-inner {\n width: 100%;\n height: 420px;\n background: #0e1120;\n position: relative;\n}\n.ols-info-section-ir-004 .ols-viewer-inner canvas {\n display: block;\n width: 100% !important;\n height: 100% !important;\n cursor: grab;\n touch-action: none;\n}\n.ols-info-section-ir-004 .ols-viewer-controls {\n background: #f9fafb;\n border-top: 1px solid #e5e7eb;\n padding: 18px 20px 14px;\n}\n.ols-info-section-ir-004 .ols-viewer-buttons {\n display: flex;\n flex-wrap: wrap;\n gap: 10px;\n justify-content: center;\n margin-bottom: 14px;\n}\n.ols-info-section-ir-004 .ols-vbtn {\n border: none;\n border-radius: 999px;\n padding: 10px 20px;\n background: #1C244B;\n color: #fff;\n font-size: 14px;\n font-family: Poppins, Arial, sans-serif;\n font-weight: 500;\n cursor: pointer;\n transition: background 0.2s, transform 0.15s;\n}\n.ols-info-section-ir-004 .ols-vbtn:hover { transform: translateY(-2px); }\n.ols-info-section-ir-004 .ols-vbtn-secondary { background: #374151; }\n.ols-info-section-ir-004 .ols-vbtn-active { background: #3B4FD4; }\n.ols-info-section-ir-004 .ols-caption {\n text-align: center;\n color: #6b7280;\n font-size: 14px;\n font-style: italic;\n margin: 0;\n min-height: 20px;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-004 .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-004 .ols-title { font-size: 24px; }\n .ols-info-section-ir-004 .ols-body { font-size: 16px; }\n .ols-info-section-ir-004 .ols-viewer-inner { height: 340px; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-004 .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-004 .ols-title { font-size: 20px; }\n .ols-info-section-ir-004 .ols-body { font-size: 15px; }\n .ols-info-section-ir-004 .ols-text-card { padding: 18px 16px; }\n .ols-info-section-ir-004 .ols-viewer-inner { height: 280px; }\n .ols-info-section-ir-004 .ols-vbtn { font-size: 13px; padding: 9px 14px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h3>Sulphur Dioxide (SO₂)<\/h3>\n<p>\n Sulphur dioxide has three different possible vibrations, each occurring at a different infrared frequency.\n <\/p>\n<p> <button id=\"ols-ir004-btn-sym\" onclick=\"olsIr004.setMode('symmetric')\">Symmetric stretch<\/button><br \/>\n <button id=\"ols-ir004-btn-asym\" onclick=\"olsIr004.setMode('asymmetric')\">Asymmetric stretch<\/button><br \/>\n <button id=\"ols-ir004-btn-bend\" onclick=\"olsIr004.setMode('bending')\">Bending vibration<\/button><br \/>\n <button id=\"ols-ir004-btn-pause\" onclick=\"olsIr004.togglePause()\">Pause<\/button><br \/>\n <button onclick=\"olsIr004.setMode('reset')\">Reset<\/button><\/p>\n<p id=\"ols-ir004-caption\">Drag the molecule to rotate. Click a vibration mode to begin.<\/p>\n<p><\/p>\n<style>\n.ols-info-section-ir-006-a * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-006-a {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-006-a .ols-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-006-a .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-006-a .ols-title {\n margin: 0 0 8px 0;\n font-size: 30px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-006-a .ols-line {\n width: 70px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-006-a .ols-stack {\n display: flex;\n flex-direction: column;\n gap: 22px;\n margin-top: 26px;\n}\n.ols-info-section-ir-006-a .ols-text-card,\n.ols-info-section-ir-006-a .ols-image-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-006-a .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0;\n}\n.ols-info-section-ir-006-a .ols-image-card img {\n width: 100%;\n display: block;\n border-radius: 14px;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-006-a .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-006-a .ols-title { font-size: 24px; }\n .ols-info-section-ir-006-a .ols-body { font-size: 16px; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-006-a .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-006-a .ols-title { font-size: 20px; }\n .ols-info-section-ir-006-a .ols-body { font-size: 15px; }\n .ols-info-section-ir-006-a .ols-text-card,\n .ols-info-section-ir-006-a .ols-image-card { padding: 18px 16px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h3>Carbon dioxide (CO\u2082)<\/h3>\n<p>\n Consequently, the infrared spectrum of carbon dioxide shows absorptions only for asymmetrical stretching and bending vibrations, while symmetrical stretching is not detected.\n <\/p>\n<p> <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/03\/infrared-spectroscopy-carbon-dioxide-spectrum.png\"\n alt=\"Infrared spectrum of carbon dioxide showing absorption peaks for asymmetrical stretching and bending vibrations\"><br \/>\n<\/p>\n<style>\n.ols-info-section-ir-005-b * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-005-b {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-005-b .ols-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-005-b .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-005-b .ols-title {\n margin: 0 0 8px 0;\n font-size: 30px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-005-b .ols-line {\n width: 70px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-005-b .ols-text-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-005-b .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0 0 14px 0;\n}\n.ols-info-section-ir-005-b .ols-body:last-child { margin-bottom: 0; }\n.ols-info-section-ir-005-b .ols-body strong {\n font-weight: 600;\n color: #1C244B;\n}\n.ols-info-section-ir-005-b .ols-viewer-wrap {\n margin-top: 28px;\n border-radius: 18px;\n overflow: hidden;\n border: 1px solid #e5e7eb;\n}\n.ols-info-section-ir-005-b .ols-viewer-inner {\n width: 100%;\n height: 420px;\n background: #0e1120;\n position: relative;\n}\n.ols-info-section-ir-005-b .ols-viewer-inner canvas {\n display: block;\n width: 100% !important;\n height: 100% !important;\n cursor: grab;\n touch-action: none;\n}\n.ols-info-section-ir-005-b .ols-viewer-controls {\n background: #f9fafb;\n border-top: 1px solid #e5e7eb;\n padding: 18px 20px 14px;\n}\n.ols-info-section-ir-005-b .ols-viewer-buttons {\n display: flex;\n flex-wrap: wrap;\n gap: 10px;\n justify-content: center;\n margin-bottom: 14px;\n}\n.ols-info-section-ir-005-b .ols-vbtn {\n border: none;\n border-radius: 999px;\n padding: 10px 20px;\n background: #1C244B;\n color: #fff;\n font-size: 14px;\n font-family: Poppins, Arial, sans-serif;\n font-weight: 500;\n cursor: pointer;\n transition: background 0.2s, transform 0.15s;\n}\n.ols-info-section-ir-005-b .ols-vbtn:hover { transform: translateY(-2px); }\n.ols-info-section-ir-005-b .ols-vbtn-secondary { background: #374151; }\n.ols-info-section-ir-005-b .ols-vbtn-active { background: #3B4FD4; }\n.ols-info-section-ir-005-b .ols-caption {\n text-align: center;\n color: #6b7280;\n font-size: 14px;\n font-style: italic;\n margin: 0;\n min-height: 20px;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-005-b .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-005-b .ols-title { font-size: 24px; }\n .ols-info-section-ir-005-b .ols-body { font-size: 16px; }\n .ols-info-section-ir-005-b .ols-viewer-inner { height: 340px; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-005-b .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-005-b .ols-title { font-size: 20px; }\n .ols-info-section-ir-005-b .ols-body { font-size: 15px; }\n .ols-info-section-ir-005-b .ols-text-card { padding: 18px 16px; }\n .ols-info-section-ir-005-b .ols-viewer-inner { height: 280px; }\n .ols-info-section-ir-005-b .ols-vbtn { font-size: 13px; padding: 9px 14px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h3>Carbon Dioxide (CO₂)<\/h3>\n<p>\n Carbon dioxide (CO₂) is a <strong>linear molecule<\/strong>, meaning its atoms lie in a straight line. Because of this symmetry, some vibrations do not cause a change in the dipole moment of the molecule.\n <\/p>\n<p>\n During <strong>symmetrical stretching<\/strong>, both C=O bonds stretch and compress at the same time. The effect on one side of the molecule is balanced by the identical effect on the other side. As a result, there is no overall change in dipole moment, so this vibration does <strong>not<\/strong> absorb infrared radiation.\n <\/p>\n<p>\n However, <strong>asymmetrical stretching<\/strong> (where one bond stretches while the other compresses) and <strong>bond bending<\/strong> both create a temporary imbalance in charge distribution. Because the dipole moment changes during these vibrations, they <strong>do<\/strong> absorb infrared radiation.\n <\/p>\n<p> <button id=\"ols-ir005-btn-sym\" onclick=\"olsIr005.setMode('symmetric')\">Symmetric stretch<\/button><br \/>\n <button id=\"ols-ir005-btn-asym\" onclick=\"olsIr005.setMode('asymmetric')\">Asymmetric stretch<\/button><br \/>\n <button id=\"ols-ir005-btn-bend\" onclick=\"olsIr005.setMode('bending')\">Bending vibration<\/button><br \/>\n <button id=\"ols-ir005-btn-pause\" onclick=\"olsIr005.togglePause()\">Pause<\/button><br \/>\n <button onclick=\"olsIr005.setMode('reset')\">Reset<\/button><\/p>\n<p id=\"ols-ir005-caption\">Drag the molecule to rotate. Click a vibration mode to begin.<\/p>\n<p><\/p>\n<style>\n.ols-info-section-ir-006-b * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-006-b {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-006-b .ols-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-006-b .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-006-b .ols-title {\n margin: 0 0 8px 0;\n font-size: 30px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-006-b .ols-line {\n width: 70px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-006-b .ols-text-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-006-b .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0 0 14px 0;\n}\n.ols-info-section-ir-006-b .ols-body:last-child { margin-bottom: 0; }\n.ols-info-section-ir-006-b .ols-body strong { font-weight: 600; color: #1C244B; }\n.ols-info-section-ir-006-b .ols-body a {\n color: #1C244B;\n text-decoration: underline;\n text-underline-offset: 2px;\n text-decoration-thickness: 1px;\n}\n.ols-info-section-ir-006-b .ols-body a:hover { opacity: 0.75; }\n.ols-info-section-ir-006-b .ols-viewer-wrap {\n margin-top: 28px;\n border-radius: 18px;\n overflow: hidden;\n border: 1px solid #e5e7eb;\n}\n.ols-info-section-ir-006-b .ols-viewer-inner {\n width: 100%;\n height: 440px;\n background: #0e1120;\n position: relative;\n}\n.ols-info-section-ir-006-b .ols-viewer-inner canvas {\n display: block;\n width: 100% !important;\n height: 100% !important;\n cursor: grab;\n touch-action: none;\n}\n.ols-info-section-ir-006-b .ols-viewer-controls {\n background: #f9fafb;\n border-top: 1px solid #e5e7eb;\n padding: 18px 20px 14px;\n}\n.ols-info-section-ir-006-b .ols-viewer-buttons {\n display: flex;\n flex-wrap: wrap;\n gap: 10px;\n justify-content: center;\n margin-bottom: 14px;\n}\n.ols-info-section-ir-006-b .ols-vbtn {\n border: none;\n border-radius: 999px;\n padding: 10px 18px;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-family: Poppins, Arial, sans-serif;\n font-weight: 500;\n cursor: pointer;\n transition: background 0.2s, transform 0.15s;\n}\n.ols-info-section-ir-006-b .ols-vbtn:hover { transform: translateY(-2px); }\n.ols-info-section-ir-006-b .ols-vbtn-secondary { background: #374151; }\n.ols-info-section-ir-006-b .ols-vbtn-active { background: #3B4FD4; }\n.ols-info-section-ir-006-b .ols-caption {\n text-align: center;\n color: #6b7280;\n font-size: 14px;\n font-style: italic;\n margin: 0;\n min-height: 20px;\n}\n.ols-info-section-ir-006-b .ols-text-card-below {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n margin-top: 28px;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-006-b .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-006-b .ols-title { font-size: 24px; }\n .ols-info-section-ir-006-b .ols-body { font-size: 16px; }\n .ols-info-section-ir-006-b .ols-viewer-inner { height: 360px; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-006-b .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-006-b .ols-title { font-size: 20px; }\n .ols-info-section-ir-006-b .ols-body { font-size: 15px; }\n .ols-info-section-ir-006-b .ols-text-card { padding: 18px 16px; }\n .ols-info-section-ir-006-b .ols-text-card-below { padding: 18px 16px; }\n .ols-info-section-ir-006-b .ols-viewer-inner { height: 300px; }\n .ols-info-section-ir-006-b .ols-vbtn { font-size: 12px; padding: 8px 12px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h3>Vibrations in Larger Molecules<\/h3>\n<p>\n As molecules become larger and more complex, the number of possible vibrational modes increases. Different parts of the molecule can move in different ways, including <strong>stretching<\/strong>, <strong>bending<\/strong>, <strong>twisting<\/strong>, and <strong>rocking<\/strong> motions.\n <\/p>\n<p>\n Each of these vibrations occurs at a specific frequency and produces its own absorption in the infrared spectrum. This means that larger molecules typically show many absorption peaks, with each peak corresponding to a particular type of molecular vibration.\n <\/p>\n<p>\n Although the number of peaks increases with molecular size, certain types of bonds absorb infrared radiation in predictable regions of the spectrum. For example, bonds such as <strong>O–H<\/strong>, <strong>C=O<\/strong>, and <strong>C–H<\/strong> absorb at characteristic frequencies regardless of the rest of the molecule.\n <\/p>\n<p> <button id=\"ols-ir006-btn-sym-str\" onclick=\"olsIr006.setMode('sym-stretch')\">Sym. stretch<\/button><br \/>\n <button id=\"ols-ir006-btn-asym-str\" onclick=\"olsIr006.setMode('asym-stretch')\">Asym. stretch<\/button><br \/>\n <button id=\"ols-ir006-btn-scissor\" onclick=\"olsIr006.setMode('scissoring')\">Scissoring<\/button><br \/>\n <button id=\"ols-ir006-btn-rock\" onclick=\"olsIr006.setMode('rocking')\">Rocking<\/button><br \/>\n <button id=\"ols-ir006-btn-wag\" onclick=\"olsIr006.setMode('wagging')\">Wagging<\/button><br \/>\n <button id=\"ols-ir006-btn-twist\" onclick=\"olsIr006.setMode('twisting')\">Twisting<\/button><br \/>\n <button id=\"ols-ir006-btn-pause\" onclick=\"olsIr006.togglePause()\">Pause<\/button><br \/>\n <button onclick=\"olsIr006.setMode('reset')\">Reset<\/button><\/p>\n<p id=\"ols-ir006-caption\">Drag the molecule to rotate. Click a vibration mode to begin.<\/p>\n<p>\n Because of this, infrared spectroscopy is extremely useful for <strong>identifying functional groups within molecules<\/strong>. By analysing the positions of absorption peaks in the infrared spectrum, chemists can determine which types of bonds — and therefore which <strong>functional groups<\/strong> — are present in a compound.\n <\/p>\n<p>\n You can read more about how chemists use this technique in the classroom in this <a href=\"https:\/\/edu.rsc.org\/resources\/infrared-ir-spectroscopy\/4010243.article\" target=\"_blank\" rel=\"noopener\">infrared spectroscopy resource from the Royal Society of Chemistry<\/a>.\n <\/p>\n<p><br \/>\n<\/p>\n<style>\n.ols-related-section-001 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-related-section-001 {\n max-width: 1100px;\n margin: 0 auto 56px auto;\n padding: 0 16px;\n}\n.ols-related-section-001 .ols-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-related-section-001 .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-related-section-001 .ols-title {\n margin: 0 0 8px 0;\n font-size: 34px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-related-section-001 .ols-line {\n width: 80px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 28px 0;\n}\n.ols-related-section-001 .ols-grid {\n display: grid;\n grid-template-columns: repeat(3, 1fr);\n gap: 22px;\n margin-top: 8px;\n}\n.ols-related-section-001 .ols-blog-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n overflow: hidden;\n display: flex;\n flex-direction: column;\n text-decoration: none;\n color: inherit;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n transition: transform 0.25s ease, box-shadow 0.25s ease;\n}\n.ols-related-section-001 .ols-blog-card:hover {\n transform: translateY(-4px);\n box-shadow: 0 12px 24px rgba(0,0,0,0.1);\n}\n.ols-related-section-001 .ols-blog-card.ols-coming-soon {\n cursor: default;\n opacity: 0.85;\n}\n.ols-related-section-001 .ols-blog-card.ols-coming-soon:hover {\n transform: none;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-related-section-001 .ols-blog-image {\n width: 100%;\n height: 180px;\n overflow: hidden;\n background: #e5e7eb;\n position: relative;\n}\n.ols-related-section-001 .ols-blog-image img {\n width: 100%;\n height: 100%;\n object-fit: cover;\n display: block;\n transition: transform 0.4s ease;\n}\n.ols-related-section-001 .ols-blog-card:hover .ols-blog-image img {\n transform: scale(1.05);\n}\n.ols-related-section-001 .ols-blog-card.ols-coming-soon:hover .ols-blog-image img {\n transform: none;\n}\n.ols-related-section-001 .ols-coming-badge {\n position: absolute;\n top: 14px;\n right: 14px;\n background: #6B1A1A;\n color: #fff;\n font-size: 12px;\n font-weight: 500;\n letter-spacing: 0.04em;\n padding: 5px 12px;\n border-radius: 999px;\n}\n.ols-related-section-001 .ols-blog-content {\n padding: 20px 22px 24px 22px;\n display: flex;\n flex-direction: column;\n flex-grow: 1;\n}\n.ols-related-section-001 .ols-blog-title {\n font-size: 18px;\n font-weight: 600;\n line-height: 1.35;\n color: #1C244B;\n margin: 0 0 12px 0;\n}\n.ols-related-section-001 .ols-blog-desc {\n font-size: 14px;\n font-weight: 300;\n line-height: 1.7;\n color: #374151;\n margin: 0 0 16px 0;\n flex-grow: 1;\n}\n.ols-related-section-001 .ols-read-more {\n font-size: 13px;\n font-weight: 500;\n color: #c81e1e;\n letter-spacing: 0.02em;\n margin-top: auto;\n}\n.ols-related-section-001 .ols-blog-card.ols-coming-soon .ols-read-more {\n color: #6b7280;\n}\n@media (max-width: 900px) {\n .ols-related-section-001 .ols-card {\n padding: 24px 20px;\n }\n .ols-related-section-001 .ols-title {\n font-size: 26px;\n }\n .ols-related-section-001 .ols-grid {\n grid-template-columns: 1fr;\n }\n .ols-related-section-001 .ols-blog-image {\n height: 200px;\n }\n}\n@media (max-width: 480px) {\n .ols-related-section-001 .ols-card {\n padding: 20px 16px;\n }\n .ols-related-section-001 .ols-title {\n font-size: 22px;\n }\n .ols-related-section-001 .ols-blog-title {\n font-size: 17px;\n }\n .ols-related-section-001 .ols-blog-desc {\n font-size: 13px;\n }\n}\n<\/style>\n<p> Continue Reading<\/p>\n<h2>Related Blogs<\/h2>\n<p> <br \/>\n <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/how-x-rays-reveal-the-structure-of-metal-crystals\/\" target=\"_blank\" rel=\"noopener\"><br \/>\n <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/03\/ChatGPT-Image-Mar-8-2026-05_43_16-PM.jpg\"\n alt=\"X-ray diffraction revealing the internal structure of a sodium chloride crystal\"><\/p>\n<h3>How X-Rays Reveal the Structure of Metal Crystals<\/h3>\n<p>\n Explore the structure of metal crystals and how X-ray diffraction reveals their atomic arrangements. Learn about common crystal lattices such as face-centred and body-centred cubic structures, and how theories like electron pair repulsion help explain the molecular shapes of sulphur compounds.\n <\/p>\n<p> Read article →<br \/>\n <\/a><br \/>\n <br \/>\n <a href=\"https:\/\/www.a-levelchemistry.co.uk\/development-of-the-modern-atomic-model.html\" target=\"_blank\" rel=\"noopener\"><br \/>\n <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Erwin-Schrodinger.webp\"\n alt=\"Erwin Schrodinger and the development of the modern atomic model\"><\/p>\n<h3>Development of the Modern Atomic Model<\/h3>\n<p>\n Trace the evolution of atomic theory from Dalton’s solid spheres to Schrodinger’s quantum mechanical model. Discover how scientists like Thomson, Rutherford, Bohr and Schrodinger transformed our understanding of atomic structure and electron behaviour through groundbreaking experiments and mathematical models.\n <\/p>\n<p> Read article →<br \/>\n <\/a><br \/>\n <br \/>\n <br \/>\n <img decoding=\"async\" src=\"REPLACE_WITH_IMAGE_URL\"\n alt=\"REPLACE_WITH_IMAGE_ALT_TEXT\"><br \/>\n Coming soon<\/p>\n<h3>REPLACE_WITH_BLOG_TITLE<\/h3>\n<p>\n REPLACE_WITH_BLOG_DESCRIPTION — a short summary of the blog post written in the same tone as the other cards above, around two to four sentences explaining what the reader will learn.\n <\/p>\n<p> Coming soon<br \/>\n<\/body><br \/>\n<\/html><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Infrared spectroscopy is one of the most powerful tools in modern chemistry, used to identify bonds, study molecular vibrations and even monitor greenhouse gases like CO\u2082 and methane. Discover how bond stretching, bending and dipole moments allow molecules to absorb infrared radiation \u2014 and why this technique is essential for A-Level Chemistry.<\/p>\n","protected":false},"author":12,"featured_media":1175,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[318],"tags":[348,357,353,359,354,349,363,361,358,350,362,351,352,355,356,360],"class_list":["post-1164","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-chemistry-a-level","tag-a-level-chemistry","tag-bending-vibrations","tag-bond-vibrations","tag-carbon-dioxide","tag-dipole-moment","tag-edexcel-chemistry","tag-electromagnetic-spectrum","tag-functional-groups","tag-greenhouse-gases","tag-ial-chemistry","tag-infrared-absorption","tag-infrared-spectroscopy","tag-ir-spectroscopy","tag-molecular-vibrations","tag-stretching-vibrations","tag-sulphur-dioxide"],"_links":{"self":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/posts\/1164","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/comments?post=1164"}],"version-history":[{"count":0,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/posts\/1164\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/media\/1175"}],"wp:attachment":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/media?parent=1164"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/categories?post=1164"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/tags?post=1164"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}

{"id":1164,"date":"2026-03-07T12:00:42","date_gmt":"2026-03-07T12:00:42","guid":{"rendered":"https:\/\/onlinelearningsystem.net\/xyz\/?p=1164"},"modified":"2026-05-03T16:23:50","modified_gmt":"2026-05-03T15:23:50","slug":"infrared-spectroscopy-a-level-chemistry","status":"publish","type":"post","link":"https:\/\/www.onlinelearningsystem.net\/xyz\/infrared-spectroscopy-a-level-chemistry\/","title":{"rendered":"Infrared Spectroscopy"},"content":{"rendered":"

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\nInfrared Spectroscopy | A Level Chemistry<\/title>\n<link href=\"https:\/\/fonts.googleapis.com\/css2?family=Poppins:wght@300;400;500;600&display=swap\" rel=\"stylesheet\">\n<style>\nbody {\n margin: 0;\n padding: 40px 0;\n background: #ffffff;\n font-family: Poppins, Arial, sans-serif;\n}\n<\/style>\n<p><\/head><br \/>\n<body><br \/>\n<\/p>\n<style>\n.ols-hero-section-blog-001 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-hero-section-blog-001 {\n max-width: 1100px;\n margin: 0 auto 56px auto;\n padding: 0 16px;\n}\n.ols-hero-section-blog-001 .ols-hero-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 26px;\n overflow: hidden;\n box-shadow: 0 10px 28px rgba(0,0,0,0.08);\n}\n.ols-hero-section-blog-001 .ols-hero-image img {\n width: 100%;\n height: 420px;\n object-fit: cover;\n display: block;\n}\n.ols-hero-section-blog-001 .ols-hero-content {\n padding: 36px 40px 40px 40px;\n}\n.ols-hero-section-blog-001 .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin-bottom: 18px;\n}\n.ols-hero-section-blog-001 .ols-title {\n font-size: 40px;\n font-weight: 600;\n line-height: 1.15;\n color: #1C244B;\n margin: 0 0 10px 0;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-hero-section-blog-001 .ols-line {\n width: 90px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 22px 0;\n}\n.ols-hero-section-blog-001 .ols-excerpt {\n font-size: 22px;\n font-weight: 300;\n line-height: 1.75;\n color: #374151;\n}\n@media (max-width: 900px) {\n .ols-hero-section-blog-001 .ols-hero-image img { height: 320px; }\n .ols-hero-section-blog-001 .ols-title { font-size: 30px; }\n .ols-hero-section-blog-001 .ols-excerpt { font-size: 18px; }\n .ols-hero-section-blog-001 .ols-hero-content { padding: 26px 24px; }\n}\n@media (max-width: 480px) {\n .ols-hero-section-blog-001 .ols-title { font-size: 24px; }\n .ols-hero-section-blog-001 .ols-excerpt { font-size: 16px; }\n}\n<\/style>\n<p> <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/03\/infrared-spectroscopy-greenhouse-effect-illustration.png\"\n alt=\"Infrared spectroscopy used to study molecular vibrations and greenhouse gases like carbon dioxide and methane\"><br \/>\n A Level Chemistry<\/p>\n<h1>Infrared Spectroscopy<\/h1>\n<p>\n Infrared spectroscopy is one of the most powerful tools in modern chemistry, used to identify bonds, study molecular vibrations and even monitor greenhouse gases like CO\u2082 and methane. Discover how bond stretching, bending and dipole moments allow molecules to absorb infrared radiation and why this technique is essential for A-Level Chemistry.\n <\/p>\n<p><\/p>\n<style>\n.ols-info-section-ir-001 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-001 {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-001 .ols-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-001 .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-001 .ols-title {\n margin: 0 0 8px 0;\n font-size: 34px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-001 .ols-line {\n width: 80px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-001 .ols-top-grid {\n display: grid;\n grid-template-columns: 1fr 1fr;\n gap: 26px;\n align-items: start;\n margin-top: 26px;\n}\n.ols-info-section-ir-001 .ols-bottom-grid {\n display: grid;\n grid-template-columns: 1fr;\n margin-top: 26px;\n}\n.ols-info-section-ir-001 .ols-text-card,\n.ols-info-section-ir-001 .ols-image-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-001 .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0 0 18px 0;\n}\n.ols-info-section-ir-001 .ols-body:last-child { margin-bottom: 0; }\n.ols-info-section-ir-001 .ols-image-card { padding: 20px; }\n.ols-info-section-ir-001 .ols-image-card img {\n width: 100%;\n display: block;\n border-radius: 14px;\n}\n.ols-info-section-ir-001 .ols-image-caption {\n margin-top: 14px;\n color: #1C244B;\n font-size: 14px;\n font-weight: 500;\n line-height: 1.4;\n text-align: center;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-001 .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-001 .ols-title { font-size: 26px; }\n .ols-info-section-ir-001 .ols-body { font-size: 16px; }\n .ols-info-section-ir-001 .ols-top-grid { grid-template-columns: 1fr; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-001 .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-001 .ols-title { font-size: 22px; }\n .ols-info-section-ir-001 .ols-body { font-size: 15px; }\n .ols-info-section-ir-001 .ols-text-card,\n .ols-info-section-ir-001 .ols-image-card { padding: 18px 16px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h2>Greenhouse Gases<\/h2>\n<p>\n Climate change affects the global environment and is strongly influenced by human activity. To limit atmospheric pollution, countries have created international agreements such as the Kyoto Protocol. These agreements aim to reduce emissions of major greenhouse gases including CO\u2082, methane (CH\u2084), nitrous oxide (N\u2082O), and ozone (O\u2083). Monitoring these gases is important for understanding their environmental impact.\n <\/p>\n<p>\n Measurements show that carbon dioxide levels in the atmosphere have increased significantly over the past 50 years. Data from ice cores indicate that before industrialisation, atmospheric CO\u2082 was about 278 ppm. Between 1000 and 1800, it varied by only about 7 ppm, showing that natural levels were relatively stable.\n <\/p>\n<p> <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/03\/infrared-spectroscopy-greenhouse-gases-diagram.png\"\n alt=\"Infrared spectroscopy diagram showing greenhouse gases including carbon dioxide, methane, nitrous oxide and ozone\"><br \/>\n Greenhouse gases absorb infrared radiation at specific wavelengths, allowing their concentrations to be monitored.<\/p>\n<p>\n However, between 1958 and 2004, atmospheric CO\u2082 increased from around 315 ppm to 378 ppm. Compared with the pre-industrial level of 278 ppm, this represents an increase of about 100 ppm, which is approximately 36% higher. This rise is largely linked to human activities such as burning fossil fuels and deforestation.\n <\/p>\n<p>\n Atmospheric gas concentrations are commonly measured using infrared spectroscopy, because greenhouse gases absorb infrared radiation at specific wavelengths. This allows scientists to detect and quantify the gases present in the atmosphere.\n <\/p>\n<p><\/p>\n<style>\n.ols-info-section-ir-002 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-002 {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-002 .ols-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-002 .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-002 .ols-title {\n margin: 0 0 8px 0;\n font-size: 34px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-002 .ols-line {\n width: 80px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-002 .ols-top-grid {\n display: grid;\n grid-template-columns: 1fr 1fr;\n gap: 26px;\n align-items: start;\n margin-top: 26px;\n}\n.ols-info-section-ir-002 .ols-bottom-grid {\n display: grid;\n grid-template-columns: 1fr;\n margin-top: 26px;\n}\n.ols-info-section-ir-002 .ols-text-card,\n.ols-info-section-ir-002 .ols-image-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-002 .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0 0 18px 0;\n}\n.ols-info-section-ir-002 .ols-body:last-child { margin-bottom: 0; }\n.ols-info-section-ir-002 .ols-body strong {\n font-weight: 600;\n color: #1C244B;\n}\n.ols-info-section-ir-002 .ols-body a {\n color: #1C244B;\n text-decoration: underline;\n text-underline-offset: 3px;\n text-decoration-thickness: 1px;\n}\n.ols-info-section-ir-002 .ols-image-card { padding: 20px; }\n.ols-info-section-ir-002 .ols-image-card img {\n width: 100%;\n display: block;\n border-radius: 14px;\n}\n.ols-info-section-ir-002 .ols-image-caption {\n margin-top: 14px;\n color: #1C244B;\n font-size: 14px;\n font-weight: 500;\n line-height: 1.4;\n text-align: center;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-002 .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-002 .ols-title { font-size: 26px; }\n .ols-info-section-ir-002 .ols-body { font-size: 16px; }\n .ols-info-section-ir-002 .ols-top-grid { grid-template-columns: 1fr; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-002 .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-002 .ols-title { font-size: 22px; }\n .ols-info-section-ir-002 .ols-body { font-size: 15px; }\n .ols-info-section-ir-002 .ols-text-card,\n .ols-info-section-ir-002 .ols-image-card { padding: 18px 16px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h2>How Molecular Bond Vibrations Produce Infrared Absorption<\/h2>\n<p>\n Even when molecules are part of a solid structure, the atoms within them are not completely still. The bonds between atoms constantly vibrate, stretching and compressing while the molecule also bends slightly. Each of these vibrations happens at a specific frequency, which depends on the atoms involved in the bond and how they are connected.\n <\/p>\n<p>\n All molecules can absorb energy. When a molecule absorbs energy that matches the vibrational energy of one of its bonds, the vibration becomes stronger. In other words, the amplitude of the vibration increases and the bond enters what is called an excited state.\n <\/p>\n<p> <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/03\/infrared-spectroscopy-dipole-moment-diagram.png\"\n alt=\"Infrared spectroscopy diagram showing molecular bond vibrations and changing dipole moment\"><br \/>\n Infrared absorption occurs when a bond vibration causes a change in dipole moment.<\/p>\n<p>\n After a short time, the molecule returns to its <strong>ground state<\/strong> and releases the absorbed energy. This energy can be detected, and because each bond vibrates at its own characteristic frequency, the detected energy provides information about the types of bonds present in the molecule. These frequencies lie in the <strong>infrared region of the electromagnetic spectrum<\/strong>, which is why this technique is called <strong>infrared (IR) spectroscopy<\/strong>.\n <\/p>\n<p>\n Like other analytical techniques such as <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/how-x-rays-reveal-the-structure-of-metal-crystals\/\" target=\"_blank\" rel=\"noopener\">X-ray diffraction<\/a>, infrared spectroscopy gives chemists a powerful way to investigate molecules and the bonds that hold them together.\n <\/p>\n<p>\n However, not every bond in a molecule will absorb infrared radiation. For absorption to occur, the vibration must cause a <strong>change in the dipole moment<\/strong> of the bond.\n <\/p>\n<p>\n A <strong>dipole moment<\/strong> exists when there is a separation of charge in a bond. It is defined as the <strong>magnitude of the charge multiplied by the distance between the charges<\/strong>. Many bonds have a dipole moment because the atoms involved have <strong>different electronegativities<\/strong>, meaning the electrons are shared unevenly. When these bonds vibrate, the dipole moment changes, allowing the bond to absorb infrared radiation.\n <\/p>\n<p>\n For a more detailed look at the underlying theory, you can explore this overview of <a href=\"https:\/\/chem.libretexts.org\/Courses\/Providence_College\/Organic_Chemistry_I\/05%3A_Analytical_Methods_for_Structure_Elucidation\/5.04%3A_Infrared_Spectroscopy\" target=\"_blank\" rel=\"noopener\">infrared spectroscopy from Chemistry LibreTexts<\/a>, which covers the same concepts at undergraduate level.\n <\/p>\n<p><\/p>\n<style>\n.ols-info-section-ir-003 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-003 {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-003 .ols-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-003 .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-003 .ols-title {\n margin: 0 0 8px 0;\n font-size: 30px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-003 .ols-line {\n width: 70px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-003 .ols-grid {\n display: grid;\n grid-template-columns: 1fr 1fr;\n gap: 26px;\n align-items: start;\n margin-top: 26px;\n}\n.ols-info-section-ir-003 .ols-text-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-003 .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0 0 18px 0;\n}\n.ols-info-section-ir-003 .ols-body:last-child { margin-bottom: 0; }\n.ols-info-section-ir-003 .ols-body strong {\n font-weight: 600;\n color: #1C244B;\n}\n.ols-info-section-ir-003 ul {\n margin: 10px 0 18px 18px;\n color: #374151;\n font-size: 18px;\n font-weight: 300;\n line-height: 1.8;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-003 .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-003 .ols-title { font-size: 24px; }\n .ols-info-section-ir-003 .ols-body,\n .ols-info-section-ir-003 ul { font-size: 16px; }\n .ols-info-section-ir-003 .ols-grid { grid-template-columns: 1fr; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-003 .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-003 .ols-title { font-size: 20px; }\n .ols-info-section-ir-003 .ols-body,\n .ols-info-section-ir-003 ul { font-size: 15px; }\n .ols-info-section-ir-003 .ols-text-card { padding: 18px 16px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h3>When Bonds Absorb Infrared Radiation<\/h3>\n<p>\n Not all molecules absorb infrared radiation. In symmetrical molecules, there may be no overall dipole moment. This can happen if there is no separation of charge, such as in diatomic molecules made from the same element, or when the dipole moments of individual bonds cancel each other out. When this occurs, infrared radiation is not absorbed.\n <\/p>\n<p>\n However, when bonds stretch or bend, the dipole moment of the molecule can change. If this change occurs during the vibration, the bond is able to absorb infrared radiation.\n <\/p>\n<p>\n Some bonds produce strong infrared absorptions, particularly polar bonds such as C\u2013O, C=O and O\u2013H. These bonds have significant differences in electronegativity between the atoms, so their dipole moments change noticeably during vibration. In contrast, non-polar bonds such as C\u2013C and C=C usually produce much weaker absorptions.\n <\/p>\n<p>\n There are two main types of molecular vibration:\n <\/p>\n<ul>\n<li>Stretching vibrations, where the bond length increases and decreases.<\/li>\n<li>Bending vibrations, where the bond angle changes.<\/li>\n<\/ul>\n<p>\n Bending vibrations require less energy than stretching vibrations, so they occur at lower energy and longer wavelengths in the infrared region.\n <\/p>\n<p>\n In planar molecules, such as sulphur dioxide (SO\u2082) and carbon dioxide (CO\u2082), infrared radiation can be absorbed through either bond stretching or bond bending vibrations.\n <\/p>\n<p><\/p>\n<style>\n.ols-cta-section-ir-001 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-cta-section-ir-001 {\n max-width: 1100px;\n margin: 0 auto 60px auto;\n padding: 0 16px;\n}\n.ols-cta-section-ir-001 .ols-cta-card {\n display: grid;\n grid-template-columns: 1.2fr 1fr;\n gap: 0;\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 26px;\n overflow: hidden;\n box-shadow: 0 12px 28px rgba(0,0,0,0.08);\n}\n.ols-cta-section-ir-001 .ols-cta-image img {\n width: 100%;\n height: 100%;\n object-fit: cover;\n display: block;\n}\n.ols-cta-section-ir-001 .ols-cta-content {\n padding: 40px 44px;\n display: flex;\n flex-direction: column;\n justify-content: center;\n}\n.ols-cta-section-ir-001 .ols-pill {\n display: inline-block;\n background: #6B1A1A;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin-bottom: 18px;\n}\n.ols-cta-section-ir-001 .ols-title {\n font-size: 34px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n margin: 0 0 12px 0;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-cta-section-ir-001 .ols-line {\n width: 80px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin-bottom: 20px;\n}\n.ols-cta-section-ir-001 .ols-desc {\n font-size: 20px;\n font-weight: 300;\n line-height: 1.8;\n color: #374151;\n margin-bottom: 28px;\n}\n.ols-cta-section-ir-001 .ols-btn {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 15px;\n font-weight: 500;\n padding: 12px 22px;\n border-radius: 999px;\n text-decoration: none;\n width: fit-content;\n transition: all 0.25s ease;\n}\n.ols-cta-section-ir-001 .ols-btn:hover {\n background: #000;\n transform: translateY(-2px);\n}\n@media (max-width: 900px) {\n .ols-cta-section-ir-001 .ols-cta-card { grid-template-columns: 1fr; }\n .ols-cta-section-ir-001 .ols-cta-image img { height: 260px; }\n .ols-cta-section-ir-001 .ols-cta-content { padding: 28px 24px; }\n .ols-cta-section-ir-001 .ols-title { font-size: 26px; }\n .ols-cta-section-ir-001 .ols-desc { font-size: 17px; }\n}\n@media (max-width: 480px) {\n .ols-cta-section-ir-001 .ols-title { font-size: 22px; }\n .ols-cta-section-ir-001 .ols-desc { font-size: 15px; }\n}\n<\/style>\n<p> <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/04\/edexcel-international-a-level-chemistry-topic-2-atomic-structure-periodic-table-course-banner.jpg\"\n alt=\"A-Level Chemistry course on covalent bonding, molecular shapes and symmetry of molecules\"><br \/>\n A Level Chemistry Course<\/p>\n<h3>Master Molecular Shapes & Covalent Bonding<\/h3>\n<p>\n Take your understanding further with our complete A-Level Chemistry course on covalent bonding, molecular geometry and the symmetry of molecules.\n <\/p>\n<p> <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/product\/covalent-bonding-shapes-of-molecules-edexcel-t3b-c\/\"><br \/>\n Explore the Course<br \/>\n <\/a><br \/>\n<\/p>\n<style>\n.ols-info-section-ir-005-a * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-005-a {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-005-a .ols-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-005-a .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-005-a .ols-title {\n margin: 0 0 8px 0;\n font-size: 30px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-005-a .ols-line {\n width: 70px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-005-a .ols-stack {\n display: flex;\n flex-direction: column;\n gap: 22px;\n margin-top: 26px;\n}\n.ols-info-section-ir-005-a .ols-text-card,\n.ols-info-section-ir-005-a .ols-image-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-005-a .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0;\n}\n.ols-info-section-ir-005-a .ols-image-card img {\n width: 100%;\n display: block;\n border-radius: 14px;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-005-a .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-005-a .ols-title { font-size: 24px; }\n .ols-info-section-ir-005-a .ols-body { font-size: 16px; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-005-a .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-005-a .ols-title { font-size: 20px; }\n .ols-info-section-ir-005-a .ols-body { font-size: 15px; }\n .ols-info-section-ir-005-a .ols-text-card,\n .ols-info-section-ir-005-a .ols-image-card { padding: 18px 16px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h3>Sulphur Dioxide (SO\u2082)<\/h3>\n<p>\n Each type of molecular vibration can cause a change in the dipole moment of the molecule. When this happens, the molecule is able to absorb infrared radiation at the frequency corresponding to that vibration. Because different vibrational motions occur at different energies, each one produces a separate absorption in the infrared spectrum.\n <\/p>\n<p>\n As a result, a molecule can show multiple absorption peaks, with each peak representing a specific type of bond vibration. For example, sulphur dioxide (SO\u2082) has three possible vibrational motions. Since each of these vibrations changes the dipole moment, all three absorb infrared radiation.\n <\/p>\n<p>\n This means the infrared spectrum of sulphur dioxide shows three distinct absorption peaks, each corresponding to one of its vibrational modes.\n <\/p>\n<p> <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/03\/infraredspectrumso2.png\"\n alt=\"Infrared spectrum of sulphur dioxide showing three absorption peaks corresponding to different vibrational modes\"><br \/>\n<\/p>\n<style>\n.ols-info-section-ir-004 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-004 {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-004 .ols-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-004 .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-radius: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-004 .ols-title {\n margin: 0 0 8px 0;\n font-size: 30px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-004 .ols-line {\n width: 70px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-004 .ols-text-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-004 .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0;\n}\n.ols-info-section-ir-004 .ols-viewer-wrap {\n margin-top: 28px;\n border-radius: 18px;\n overflow: hidden;\n border: 1px solid #e5e7eb;\n}\n.ols-info-section-ir-004 .ols-viewer-inner {\n width: 100%;\n height: 420px;\n background: #0e1120;\n position: relative;\n}\n.ols-info-section-ir-004 .ols-viewer-inner canvas {\n display: block;\n width: 100% !important;\n height: 100% !important;\n cursor: grab;\n touch-action: none;\n}\n.ols-info-section-ir-004 .ols-viewer-controls {\n background: #f9fafb;\n border-top: 1px solid #e5e7eb;\n padding: 18px 20px 14px;\n}\n.ols-info-section-ir-004 .ols-viewer-buttons {\n display: flex;\n flex-wrap: wrap;\n gap: 10px;\n justify-content: center;\n margin-bottom: 14px;\n}\n.ols-info-section-ir-004 .ols-vbtn {\n border: none;\n border-radius: 999px;\n padding: 10px 20px;\n background: #1C244B;\n color: #fff;\n font-size: 14px;\n font-family: Poppins, Arial, sans-serif;\n font-weight: 500;\n cursor: pointer;\n transition: background 0.2s, transform 0.15s;\n}\n.ols-info-section-ir-004 .ols-vbtn:hover { transform: translateY(-2px); }\n.ols-info-section-ir-004 .ols-vbtn-secondary { background: #374151; }\n.ols-info-section-ir-004 .ols-vbtn-active { background: #3B4FD4; }\n.ols-info-section-ir-004 .ols-caption {\n text-align: center;\n color: #6b7280;\n font-size: 14px;\n font-style: italic;\n margin: 0;\n min-height: 20px;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-004 .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-004 .ols-title { font-size: 24px; }\n .ols-info-section-ir-004 .ols-body { font-size: 16px; }\n .ols-info-section-ir-004 .ols-viewer-inner { height: 340px; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-004 .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-004 .ols-title { font-size: 20px; }\n .ols-info-section-ir-004 .ols-body { font-size: 15px; }\n .ols-info-section-ir-004 .ols-text-card { padding: 18px 16px; }\n .ols-info-section-ir-004 .ols-viewer-inner { height: 280px; }\n .ols-info-section-ir-004 .ols-vbtn { font-size: 13px; padding: 9px 14px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h3>Sulphur Dioxide (SO₂)<\/h3>\n<p>\n Sulphur dioxide has three different possible vibrations, each occurring at a different infrared frequency.\n <\/p>\n<p> <button id=\"ols-ir004-btn-sym\" onclick=\"olsIr004.setMode('symmetric')\">Symmetric stretch<\/button><br \/>\n <button id=\"ols-ir004-btn-asym\" onclick=\"olsIr004.setMode('asymmetric')\">Asymmetric stretch<\/button><br \/>\n <button id=\"ols-ir004-btn-bend\" onclick=\"olsIr004.setMode('bending')\">Bending vibration<\/button><br \/>\n <button id=\"ols-ir004-btn-pause\" onclick=\"olsIr004.togglePause()\">Pause<\/button><br \/>\n <button onclick=\"olsIr004.setMode('reset')\">Reset<\/button><\/p>\n<p id=\"ols-ir004-caption\">Drag the molecule to rotate. Click a vibration mode to begin.<\/p>\n<p><\/p>\n<style>\n.ols-info-section-ir-006-a * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-006-a {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-006-a .ols-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-006-a .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-006-a .ols-title {\n margin: 0 0 8px 0;\n font-size: 30px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-006-a .ols-line {\n width: 70px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-006-a .ols-stack {\n display: flex;\n flex-direction: column;\n gap: 22px;\n margin-top: 26px;\n}\n.ols-info-section-ir-006-a .ols-text-card,\n.ols-info-section-ir-006-a .ols-image-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-006-a .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0;\n}\n.ols-info-section-ir-006-a .ols-image-card img {\n width: 100%;\n display: block;\n border-radius: 14px;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-006-a .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-006-a .ols-title { font-size: 24px; }\n .ols-info-section-ir-006-a .ols-body { font-size: 16px; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-006-a .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-006-a .ols-title { font-size: 20px; }\n .ols-info-section-ir-006-a .ols-body { font-size: 15px; }\n .ols-info-section-ir-006-a .ols-text-card,\n .ols-info-section-ir-006-a .ols-image-card { padding: 18px 16px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h3>Carbon dioxide (CO\u2082)<\/h3>\n<p>\n Consequently, the infrared spectrum of carbon dioxide shows absorptions only for asymmetrical stretching and bending vibrations, while symmetrical stretching is not detected.\n <\/p>\n<p> <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/03\/infrared-spectroscopy-carbon-dioxide-spectrum.png\"\n alt=\"Infrared spectrum of carbon dioxide showing absorption peaks for asymmetrical stretching and bending vibrations\"><br \/>\n<\/p>\n<style>\n.ols-info-section-ir-005-b * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-005-b {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-005-b .ols-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-005-b .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-005-b .ols-title {\n margin: 0 0 8px 0;\n font-size: 30px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-005-b .ols-line {\n width: 70px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-005-b .ols-text-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-005-b .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0 0 14px 0;\n}\n.ols-info-section-ir-005-b .ols-body:last-child { margin-bottom: 0; }\n.ols-info-section-ir-005-b .ols-body strong {\n font-weight: 600;\n color: #1C244B;\n}\n.ols-info-section-ir-005-b .ols-viewer-wrap {\n margin-top: 28px;\n border-radius: 18px;\n overflow: hidden;\n border: 1px solid #e5e7eb;\n}\n.ols-info-section-ir-005-b .ols-viewer-inner {\n width: 100%;\n height: 420px;\n background: #0e1120;\n position: relative;\n}\n.ols-info-section-ir-005-b .ols-viewer-inner canvas {\n display: block;\n width: 100% !important;\n height: 100% !important;\n cursor: grab;\n touch-action: none;\n}\n.ols-info-section-ir-005-b .ols-viewer-controls {\n background: #f9fafb;\n border-top: 1px solid #e5e7eb;\n padding: 18px 20px 14px;\n}\n.ols-info-section-ir-005-b .ols-viewer-buttons {\n display: flex;\n flex-wrap: wrap;\n gap: 10px;\n justify-content: center;\n margin-bottom: 14px;\n}\n.ols-info-section-ir-005-b .ols-vbtn {\n border: none;\n border-radius: 999px;\n padding: 10px 20px;\n background: #1C244B;\n color: #fff;\n font-size: 14px;\n font-family: Poppins, Arial, sans-serif;\n font-weight: 500;\n cursor: pointer;\n transition: background 0.2s, transform 0.15s;\n}\n.ols-info-section-ir-005-b .ols-vbtn:hover { transform: translateY(-2px); }\n.ols-info-section-ir-005-b .ols-vbtn-secondary { background: #374151; }\n.ols-info-section-ir-005-b .ols-vbtn-active { background: #3B4FD4; }\n.ols-info-section-ir-005-b .ols-caption {\n text-align: center;\n color: #6b7280;\n font-size: 14px;\n font-style: italic;\n margin: 0;\n min-height: 20px;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-005-b .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-005-b .ols-title { font-size: 24px; }\n .ols-info-section-ir-005-b .ols-body { font-size: 16px; }\n .ols-info-section-ir-005-b .ols-viewer-inner { height: 340px; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-005-b .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-005-b .ols-title { font-size: 20px; }\n .ols-info-section-ir-005-b .ols-body { font-size: 15px; }\n .ols-info-section-ir-005-b .ols-text-card { padding: 18px 16px; }\n .ols-info-section-ir-005-b .ols-viewer-inner { height: 280px; }\n .ols-info-section-ir-005-b .ols-vbtn { font-size: 13px; padding: 9px 14px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h3>Carbon Dioxide (CO₂)<\/h3>\n<p>\n Carbon dioxide (CO₂) is a <strong>linear molecule<\/strong>, meaning its atoms lie in a straight line. Because of this symmetry, some vibrations do not cause a change in the dipole moment of the molecule.\n <\/p>\n<p>\n During <strong>symmetrical stretching<\/strong>, both C=O bonds stretch and compress at the same time. The effect on one side of the molecule is balanced by the identical effect on the other side. As a result, there is no overall change in dipole moment, so this vibration does <strong>not<\/strong> absorb infrared radiation.\n <\/p>\n<p>\n However, <strong>asymmetrical stretching<\/strong> (where one bond stretches while the other compresses) and <strong>bond bending<\/strong> both create a temporary imbalance in charge distribution. Because the dipole moment changes during these vibrations, they <strong>do<\/strong> absorb infrared radiation.\n <\/p>\n<p> <button id=\"ols-ir005-btn-sym\" onclick=\"olsIr005.setMode('symmetric')\">Symmetric stretch<\/button><br \/>\n <button id=\"ols-ir005-btn-asym\" onclick=\"olsIr005.setMode('asymmetric')\">Asymmetric stretch<\/button><br \/>\n <button id=\"ols-ir005-btn-bend\" onclick=\"olsIr005.setMode('bending')\">Bending vibration<\/button><br \/>\n <button id=\"ols-ir005-btn-pause\" onclick=\"olsIr005.togglePause()\">Pause<\/button><br \/>\n <button onclick=\"olsIr005.setMode('reset')\">Reset<\/button><\/p>\n<p id=\"ols-ir005-caption\">Drag the molecule to rotate. Click a vibration mode to begin.<\/p>\n<p><\/p>\n<style>\n.ols-info-section-ir-006-b * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-info-section-ir-006-b {\n max-width: 1100px;\n margin: 0 auto 48px auto;\n padding: 0 16px;\n}\n.ols-info-section-ir-006-b .ols-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-info-section-ir-006-b .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-info-section-ir-006-b .ols-title {\n margin: 0 0 8px 0;\n font-size: 30px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-info-section-ir-006-b .ols-line {\n width: 70px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 24px 0;\n}\n.ols-info-section-ir-006-b .ols-text-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-info-section-ir-006-b .ols-body {\n font-size: 18px;\n font-weight: 300;\n line-height: 1.9;\n color: #374151;\n margin: 0 0 14px 0;\n}\n.ols-info-section-ir-006-b .ols-body:last-child { margin-bottom: 0; }\n.ols-info-section-ir-006-b .ols-body strong { font-weight: 600; color: #1C244B; }\n.ols-info-section-ir-006-b .ols-body a {\n color: #1C244B;\n text-decoration: underline;\n text-underline-offset: 2px;\n text-decoration-thickness: 1px;\n}\n.ols-info-section-ir-006-b .ols-body a:hover { opacity: 0.75; }\n.ols-info-section-ir-006-b .ols-viewer-wrap {\n margin-top: 28px;\n border-radius: 18px;\n overflow: hidden;\n border: 1px solid #e5e7eb;\n}\n.ols-info-section-ir-006-b .ols-viewer-inner {\n width: 100%;\n height: 440px;\n background: #0e1120;\n position: relative;\n}\n.ols-info-section-ir-006-b .ols-viewer-inner canvas {\n display: block;\n width: 100% !important;\n height: 100% !important;\n cursor: grab;\n touch-action: none;\n}\n.ols-info-section-ir-006-b .ols-viewer-controls {\n background: #f9fafb;\n border-top: 1px solid #e5e7eb;\n padding: 18px 20px 14px;\n}\n.ols-info-section-ir-006-b .ols-viewer-buttons {\n display: flex;\n flex-wrap: wrap;\n gap: 10px;\n justify-content: center;\n margin-bottom: 14px;\n}\n.ols-info-section-ir-006-b .ols-vbtn {\n border: none;\n border-radius: 999px;\n padding: 10px 18px;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-family: Poppins, Arial, sans-serif;\n font-weight: 500;\n cursor: pointer;\n transition: background 0.2s, transform 0.15s;\n}\n.ols-info-section-ir-006-b .ols-vbtn:hover { transform: translateY(-2px); }\n.ols-info-section-ir-006-b .ols-vbtn-secondary { background: #374151; }\n.ols-info-section-ir-006-b .ols-vbtn-active { background: #3B4FD4; }\n.ols-info-section-ir-006-b .ols-caption {\n text-align: center;\n color: #6b7280;\n font-size: 14px;\n font-style: italic;\n margin: 0;\n min-height: 20px;\n}\n.ols-info-section-ir-006-b .ols-text-card-below {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n padding: 22px 24px;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n margin-top: 28px;\n}\n@media (max-width: 900px) {\n .ols-info-section-ir-006-b .ols-card { padding: 24px 20px; }\n .ols-info-section-ir-006-b .ols-title { font-size: 24px; }\n .ols-info-section-ir-006-b .ols-body { font-size: 16px; }\n .ols-info-section-ir-006-b .ols-viewer-inner { height: 360px; }\n}\n@media (max-width: 480px) {\n .ols-info-section-ir-006-b .ols-card { padding: 20px 16px; }\n .ols-info-section-ir-006-b .ols-title { font-size: 20px; }\n .ols-info-section-ir-006-b .ols-body { font-size: 15px; }\n .ols-info-section-ir-006-b .ols-text-card { padding: 18px 16px; }\n .ols-info-section-ir-006-b .ols-text-card-below { padding: 18px 16px; }\n .ols-info-section-ir-006-b .ols-viewer-inner { height: 300px; }\n .ols-info-section-ir-006-b .ols-vbtn { font-size: 12px; padding: 8px 12px; }\n}\n<\/style>\n<p> Infrared Spectroscopy<\/p>\n<h3>Vibrations in Larger Molecules<\/h3>\n<p>\n As molecules become larger and more complex, the number of possible vibrational modes increases. Different parts of the molecule can move in different ways, including <strong>stretching<\/strong>, <strong>bending<\/strong>, <strong>twisting<\/strong>, and <strong>rocking<\/strong> motions.\n <\/p>\n<p>\n Each of these vibrations occurs at a specific frequency and produces its own absorption in the infrared spectrum. This means that larger molecules typically show many absorption peaks, with each peak corresponding to a particular type of molecular vibration.\n <\/p>\n<p>\n Although the number of peaks increases with molecular size, certain types of bonds absorb infrared radiation in predictable regions of the spectrum. For example, bonds such as <strong>O–H<\/strong>, <strong>C=O<\/strong>, and <strong>C–H<\/strong> absorb at characteristic frequencies regardless of the rest of the molecule.\n <\/p>\n<p> <button id=\"ols-ir006-btn-sym-str\" onclick=\"olsIr006.setMode('sym-stretch')\">Sym. stretch<\/button><br \/>\n <button id=\"ols-ir006-btn-asym-str\" onclick=\"olsIr006.setMode('asym-stretch')\">Asym. stretch<\/button><br \/>\n <button id=\"ols-ir006-btn-scissor\" onclick=\"olsIr006.setMode('scissoring')\">Scissoring<\/button><br \/>\n <button id=\"ols-ir006-btn-rock\" onclick=\"olsIr006.setMode('rocking')\">Rocking<\/button><br \/>\n <button id=\"ols-ir006-btn-wag\" onclick=\"olsIr006.setMode('wagging')\">Wagging<\/button><br \/>\n <button id=\"ols-ir006-btn-twist\" onclick=\"olsIr006.setMode('twisting')\">Twisting<\/button><br \/>\n <button id=\"ols-ir006-btn-pause\" onclick=\"olsIr006.togglePause()\">Pause<\/button><br \/>\n <button onclick=\"olsIr006.setMode('reset')\">Reset<\/button><\/p>\n<p id=\"ols-ir006-caption\">Drag the molecule to rotate. Click a vibration mode to begin.<\/p>\n<p>\n Because of this, infrared spectroscopy is extremely useful for <strong>identifying functional groups within molecules<\/strong>. By analysing the positions of absorption peaks in the infrared spectrum, chemists can determine which types of bonds — and therefore which <strong>functional groups<\/strong> — are present in a compound.\n <\/p>\n<p>\n You can read more about how chemists use this technique in the classroom in this <a href=\"https:\/\/edu.rsc.org\/resources\/infrared-ir-spectroscopy\/4010243.article\" target=\"_blank\" rel=\"noopener\">infrared spectroscopy resource from the Royal Society of Chemistry<\/a>.\n <\/p>\n<p><br \/>\n<\/p>\n<style>\n.ols-related-section-001 * {\n box-sizing: border-box;\n font-family: Poppins, Arial, sans-serif;\n}\n.ols-related-section-001 {\n max-width: 1100px;\n margin: 0 auto 56px auto;\n padding: 0 16px;\n}\n.ols-related-section-001 .ols-card {\n background: #F3F4F6;\n border: 1px solid #e5e7eb;\n border-radius: 24px;\n padding: 36px 40px;\n box-shadow: 0 7px 18px rgba(0,0,0,0.07);\n}\n.ols-related-section-001 .ols-pill {\n display: inline-block;\n background: #1C244B;\n color: #fff;\n font-size: 13px;\n font-weight: 500;\n letter-spacing: 0.04em;\n border-radius: 999px;\n padding: 6px 14px;\n margin: 0 0 20px 0;\n}\n.ols-related-section-001 .ols-title {\n margin: 0 0 8px 0;\n font-size: 34px;\n font-weight: 600;\n line-height: 1.2;\n color: #1C244B;\n text-shadow: -9px 0 9px rgba(28,36,75,0.3);\n}\n.ols-related-section-001 .ols-line {\n width: 80px;\n height: 4px;\n background: #c81e1e;\n border-radius: 999px;\n margin: 0 0 28px 0;\n}\n.ols-related-section-001 .ols-grid {\n display: grid;\n grid-template-columns: repeat(3, 1fr);\n gap: 22px;\n margin-top: 8px;\n}\n.ols-related-section-001 .ols-blog-card {\n background: #ffffff;\n border: 1px solid #e5e7eb;\n border-radius: 18px;\n overflow: hidden;\n display: flex;\n flex-direction: column;\n text-decoration: none;\n color: inherit;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n transition: transform 0.25s ease, box-shadow 0.25s ease;\n}\n.ols-related-section-001 .ols-blog-card:hover {\n transform: translateY(-4px);\n box-shadow: 0 12px 24px rgba(0,0,0,0.1);\n}\n.ols-related-section-001 .ols-blog-card.ols-coming-soon {\n cursor: default;\n opacity: 0.85;\n}\n.ols-related-section-001 .ols-blog-card.ols-coming-soon:hover {\n transform: none;\n box-shadow: 0 4px 14px rgba(0,0,0,0.06);\n}\n.ols-related-section-001 .ols-blog-image {\n width: 100%;\n height: 180px;\n overflow: hidden;\n background: #e5e7eb;\n position: relative;\n}\n.ols-related-section-001 .ols-blog-image img {\n width: 100%;\n height: 100%;\n object-fit: cover;\n display: block;\n transition: transform 0.4s ease;\n}\n.ols-related-section-001 .ols-blog-card:hover .ols-blog-image img {\n transform: scale(1.05);\n}\n.ols-related-section-001 .ols-blog-card.ols-coming-soon:hover .ols-blog-image img {\n transform: none;\n}\n.ols-related-section-001 .ols-coming-badge {\n position: absolute;\n top: 14px;\n right: 14px;\n background: #6B1A1A;\n color: #fff;\n font-size: 12px;\n font-weight: 500;\n letter-spacing: 0.04em;\n padding: 5px 12px;\n border-radius: 999px;\n}\n.ols-related-section-001 .ols-blog-content {\n padding: 20px 22px 24px 22px;\n display: flex;\n flex-direction: column;\n flex-grow: 1;\n}\n.ols-related-section-001 .ols-blog-title {\n font-size: 18px;\n font-weight: 600;\n line-height: 1.35;\n color: #1C244B;\n margin: 0 0 12px 0;\n}\n.ols-related-section-001 .ols-blog-desc {\n font-size: 14px;\n font-weight: 300;\n line-height: 1.7;\n color: #374151;\n margin: 0 0 16px 0;\n flex-grow: 1;\n}\n.ols-related-section-001 .ols-read-more {\n font-size: 13px;\n font-weight: 500;\n color: #c81e1e;\n letter-spacing: 0.02em;\n margin-top: auto;\n}\n.ols-related-section-001 .ols-blog-card.ols-coming-soon .ols-read-more {\n color: #6b7280;\n}\n@media (max-width: 900px) {\n .ols-related-section-001 .ols-card {\n padding: 24px 20px;\n }\n .ols-related-section-001 .ols-title {\n font-size: 26px;\n }\n .ols-related-section-001 .ols-grid {\n grid-template-columns: 1fr;\n }\n .ols-related-section-001 .ols-blog-image {\n height: 200px;\n }\n}\n@media (max-width: 480px) {\n .ols-related-section-001 .ols-card {\n padding: 20px 16px;\n }\n .ols-related-section-001 .ols-title {\n font-size: 22px;\n }\n .ols-related-section-001 .ols-blog-title {\n font-size: 17px;\n }\n .ols-related-section-001 .ols-blog-desc {\n font-size: 13px;\n }\n}\n<\/style>\n<p> Continue Reading<\/p>\n<h2>Related Blogs<\/h2>\n<p> <br \/>\n <a href=\"https:\/\/www.onlinelearningsystem.net\/xyz\/how-x-rays-reveal-the-structure-of-metal-crystals\/\" target=\"_blank\" rel=\"noopener\"><br \/>\n <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/03\/ChatGPT-Image-Mar-8-2026-05_43_16-PM.jpg\"\n alt=\"X-ray diffraction revealing the internal structure of a sodium chloride crystal\"><\/p>\n<h3>How X-Rays Reveal the Structure of Metal Crystals<\/h3>\n<p>\n Explore the structure of metal crystals and how X-ray diffraction reveals their atomic arrangements. Learn about common crystal lattices such as face-centred and body-centred cubic structures, and how theories like electron pair repulsion help explain the molecular shapes of sulphur compounds.\n <\/p>\n<p> Read article →<br \/>\n <\/a><br \/>\n <br \/>\n <a href=\"https:\/\/www.a-levelchemistry.co.uk\/development-of-the-modern-atomic-model.html\" target=\"_blank\" rel=\"noopener\"><br \/>\n <img decoding=\"async\" src=\"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-content\/uploads\/2026\/05\/Erwin-Schrodinger.webp\"\n alt=\"Erwin Schrodinger and the development of the modern atomic model\"><\/p>\n<h3>Development of the Modern Atomic Model<\/h3>\n<p>\n Trace the evolution of atomic theory from Dalton’s solid spheres to Schrodinger’s quantum mechanical model. Discover how scientists like Thomson, Rutherford, Bohr and Schrodinger transformed our understanding of atomic structure and electron behaviour through groundbreaking experiments and mathematical models.\n <\/p>\n<p> Read article →<br \/>\n <\/a><br \/>\n <br \/>\n <br \/>\n <img decoding=\"async\" src=\"REPLACE_WITH_IMAGE_URL\"\n alt=\"REPLACE_WITH_IMAGE_ALT_TEXT\"><br \/>\n Coming soon<\/p>\n<h3>REPLACE_WITH_BLOG_TITLE<\/h3>\n<p>\n REPLACE_WITH_BLOG_DESCRIPTION — a short summary of the blog post written in the same tone as the other cards above, around two to four sentences explaining what the reader will learn.\n <\/p>\n<p> Coming soon<br \/>\n<\/body><br \/>\n<\/html><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Infrared spectroscopy is one of the most powerful tools in modern chemistry, used to identify bonds, study molecular vibrations and even monitor greenhouse gases like CO\u2082 and methane. Discover how bond stretching, bending and dipole moments allow molecules to absorb infrared radiation \u2014 and why this technique is essential for A-Level Chemistry.<\/p>\n","protected":false},"author":12,"featured_media":1175,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[318],"tags":[348,357,353,359,354,349,363,361,358,350,362,351,352,355,356,360],"class_list":["post-1164","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-chemistry-a-level","tag-a-level-chemistry","tag-bending-vibrations","tag-bond-vibrations","tag-carbon-dioxide","tag-dipole-moment","tag-edexcel-chemistry","tag-electromagnetic-spectrum","tag-functional-groups","tag-greenhouse-gases","tag-ial-chemistry","tag-infrared-absorption","tag-infrared-spectroscopy","tag-ir-spectroscopy","tag-molecular-vibrations","tag-stretching-vibrations","tag-sulphur-dioxide"],"_links":{"self":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/posts\/1164","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/comments?post=1164"}],"version-history":[{"count":0,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/posts\/1164\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/media\/1175"}],"wp:attachment":[{"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/media?parent=1164"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/categories?post=1164"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.onlinelearningsystem.net\/xyz\/wp-json\/wp\/v2\/tags?post=1164"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}