2.8 MOLECULES
Many of the common molecules are composed of groups of atoms that are bound
together by strong covalent bonds; these include elemental diatomic molecules
as well as a host of compounds
In the condensed liquid and solid states, bonds between molecules are weak secondary
ones. Consequently, molecular materials have relatively low melting and
boiling temperatures. Most of those that have small molecules composed of a few
atoms are gases at ordinary, or ambient, temperatures and pressures. On the other
hand, many of the modern polymers, being molecular materials composed of
extremely large molecules, exist as solids; some of their properties are strongly
dependent on the presence of van der Waals and hydrogen secondary bonds.