Explain how a covalent bond is formed when a pair of electrons is shared between two atoms

Recall that covalent bonding results in the formation of molecules

Recall the typical size (order of magnitude) of atoms and small molecules

Explain the formation of simple molecular, covalent substances, using dot and cross diagrams, including:

a) hydrogen
b) hydrogen chloride
c) water
d) methane
e) oxygen
f) carbon dioxide