They contain no molecules. The glue which holds the ions together is a strong electrical attraction between ions of opposite charge. Covalent bonds are formed when 2 atoms share 1 or more pairs of electrons achieving the lowest possible energy. In general, covalent bonds are formed between nonmetal atoms. The lone pairs of electrons are shown as pairs of dots on individual atoms.
Many molecules obey what is known as the octet rule.
That is, when atoms form covalent bonds there is a tendency to share enough electrons so that each atom is surrounded by 8 electrons. More than 4 positions are available for bonding. Must determine enough of structure so that you know which atoms are bonded to which atoms. This comes from experience and me. It is very unusual for oxygen atoms to bond together.