Understand that calcium hydride is a binary compound formed between calcium (Ca) and hydrogen (H).
Recall that calcium is an alkaline earth metal in Group 2 of the periodic table, which means it typically forms a +2 charge as a cation (Ca^{2+}).
Hydrogen, when forming hydrides, usually gains one electron to become H^{-} with a -1 charge.
To balance the charges in the compound, two hydride ions (each with a -1 charge) are needed to balance one calcium ion (with a +2 charge), resulting in the formula CaH_{2}.
Therefore, the correct formula for calcium hydride is CaH_{2}, reflecting the charge balance between Ca^{2+} and 2 H^{-} ions.