Covalent or Molecular Hydride

Covalent Hydrides

Dihydrogen forms molecular compounds with most p-block elements — familiar examples include $CH_4$, $NH_3$, $H_2O$ and $HF$ (hydrogen compounds of non-metals are conventionally grouped here as "hydrides" too). Being covalent, these compounds are volatile.

Based on the number of electrons and bonds in their Lewis structures, molecular hydrides split further into three sub-types.

1. Electron-deficient hydrides — too few electrons to draw a conventional Lewis structure. Diborane, $B_2H_6$, is the classic example; all Group 13 elements form this type. Such compounds act as Lewis acids (electron acceptors).

2. Electron-precise hydrides — exactly the right number of electrons for a standard Lewis structure. All Group 14 elements form these (e.g. $CH_4$), which adopt tetrahedral geometry. …