Which of the following is an example of an ionic hydride?

Ionic hydrides are compounds formed between hydrogen and a metal that typically have a high electronegativity difference, resulting in ionic bonding. In this context, sodium hydride (NaH) and magnesium hydride (MgH₂) are both considered ionic hydrides due to their formation of ionic bonds between the metal and hydride, with metals from groups that readily lose electrons.

The correct choice of sodium hydride highlights an important aspect of ionic hydrides. Sodium, being an alkali metal, easily donates its electron to form Na⁺ ions, while hydrogen in this compound exists in the form of the hydride ion (H⁻). This significant charge separation confirms its ionic character.

In contrast, the other options do not qualify as ionic hydrides. CsF, for instance, is a fluoride, not a hydride. While KBr is a bromide, it does not involve hydrogen. Therefore, recognizing the characteristics of ionic bonds and the specific composition of the compound helps identify sodium hydride as a clear example of an ionic hydride.