Chemical Bonding — Scientific Principles

Scientific Principles

Identify the particles and arrangement

Sodium chloride is an extended ionic crystal. Its formula records an ion ratio rather than a detached two-atom molecule in the solid. The solid contains charges, but they are not freely mobile. In the melt, mobile ions support conduction. Do not substitute a metallic electron mechanism or assume that every ionic compound dissolves readily.

Add geometry to bond polarity

Unequal electron sharing can make a covalent bond polar. The molecular dipole depends on how the bond contributions combine. Linear carbon dioxide has cancelling opposing contributions; bent water has a net dipole. Counting polar bonds without considering their directions is insufficient.

Count lone pairs before naming shape

Water has two bonding pairs and two lone pairs around oxygen in the introductory Lewis picture. Its electron-domain arrangement is approximately tetrahedral, but its molecular shape is bent. Methane is tetrahedral and ammonia is trigonal pyramidal. Molecular shape names describe atomic positions, while lone pairs remain part of the explanation.

Separate internal bonds from intermolecular attractions

Boiling water overcomes attractions between molecules without ordinarily breaking each molecule's covalent O–H bonds. Diamond and graphite show another structural distinction: the same element can form a three-dimensional network or layered structure with different electronic behaviour. Use the particular arrangement to explain hardness or conduction instead of relying on a universal slogan about covalent substances.