According to the general definition, every element of the periodic table (except some noble gases) forms one or more hydrides. These substances have been classified into three main types according to the nature of their bonding:
*Ionic hydrides, which have significant ionic bonding character.
*Covalent hydrides, which include the hydrocarbons and many other compounds which covalently bond to hydrogen atoms.
*Interstitial hydrides, which may be described as having metallic bonding.
While these divisions have not been used universally, they are still useful to understand differences in hydrides.