Discrete atoms are atoms that form extremely weak intermolecular forces, explains the BBC. Because of this property, molecules formed from discrete atoms have very low boiling and melting points.
Molecules formed by discrete atoms, like all other covalent molecules, are held together by covalent forces. These forces are called Van Der Waals forces. Between discrete atoms, Van Der Waals forces are the only forces operating on an intermolecular level. These forces are very weak when they exist in molecules formed by the binding of discrete atoms. This gives discrete atoms the unique property of extremely low boiling and melting points because they can be separated with little energy expended.