The chemical formula for chromium(III) phosphide is CrP. Here's why:

* Chromium(III) indicates that chromium has a +3 charge (Cr³⁺).

* Phosphide refers to the phosphide anion, which has a -3 charge (P³⁻).

Since the charges are equal and opposite, they cancel each other out, resulting in a simple 1:1 ratio in the compound.