Virtual Lessons

Lesson 1 of 2

Covalent Bonding

This virtual lesson covers the nature of covalent bonding, how covalent substances are represented and structured, and the concepts of electronegativity, bond polarity, and polar molecules.

The lesson opens by establishing covalent bonding as the strong electrostatic attraction between two nuclei and a shared pair of electrons between them. Evidence for this model is drawn from the physical properties of giant atomic structures and from electron density maps for simple molecules, which confirm the concentration of electron density between bonded atoms.

The lesson then covers how to draw dot-and-cross diagrams for covalent substances, including molecules containing single, double, and triple bonds, and species involving dative covalent (coordinate) bonds such as Al2Cl6 and the ammonium ion. The giant lattice structures formed by carbon atoms are also examined, comparing the properties and applications of graphite, diamond, and graphene.

The concept of electronegativity is introduced, explaining how differences in electronegativity between bonded atoms give rise to bond polarity. Ionic and covalent bonding are presented as the extremes of a continuum of bonding type, with increasing electronegativity difference leading progressively from pure covalent through polar covalent to ionic bonding.

The lesson concludes by distinguishing between polar bonds and polar molecules, and how to predict whether a given molecule is likely to be polar overall by considering both bond polarities and molecular geometry. This links directly to the study of intermolecular forces and physical properties in subsequent lessons.