Covalent compounds
compounds which contain covalent bonds are called covalent compounds. They tend to be non-metallic and have low melting and boiling points.
Covalent hydride
a compound formed from a nonmetal and hydrogen, for example, H2S and NH3.
Crystalline
Denoting a substances that form crystals. Crystalline substances have a regular internal arrangement of atoms, even though they may not examists is geometrically regular crystals. For instance, lead (and other metals) are crystalline.


