Virtual Lessons

Lesson 4 of 5

Ionisation Energy Part 2

This virtual lesson develops a detailed understanding of the modern atomic model, atomic orbitals, electronic configuration, and ionisation energies, showing how these concepts explain the periodic properties of the elements.

The lesson begins with atomic orbitals and electronic configuration. It introduces the modern atomic model, describes the shapes of s and p orbitals, and explains how electrons fill orbitals. The rules for filling orbitals are developed, including that each orbital can hold up to two electrons with opposite spins, that orbitals within a sub-shell are occupied singly before pairing begins, and that paired electrons have opposite spin.

The lesson then covers electronic configurations for atoms from hydrogen to krypton and their ions, using both s, p, d notation and electrons-in-boxes notation. It explains how electronic configuration determines the chemical properties of an element and how the Periodic Table is divided into s, p, and d blocks.

The second and third parts focus on ionisation energy. First, second, and third ionisation energies are defined, and all ionisation energies are established as endothermic processes. The main factors affecting ionisation energy are examined, including the number of protons in the nucleus, electron shielding, atomic radius, and the sub-shell from which the electron is removed.

The lesson concludes by using ionisation energy data to explain periodic trends. Successive ionisation energies provide evidence for quantum shells and group number, while first ionisation energies across successive elements provide evidence for sub-shells. Trends in first ionisation energy across periods and down groups are explained, including the roles of nuclear charge, shielding, atomic radius, and sub-shell structure.