The gas phosphine (ph3) is used as a fumigant to protect stored grain and other durable produce from pests. phosphine is generated where it is to be used by adding water to aluminum phosphide or magnesium phosphide. give formulas for these two phosphides.

The element phosphorous belongs to group 5 of the periodic table and these elements have 3 spaces for electrons in their compounds.

In the case of aluminum, the formula will be:

AlP, because Al forms an ion with a charge of +3.

In the case of magnesium, the formula will be:
Mg₃P₂ because magnesium forms an ion with a charge of +2

Talc (french chalk) is the ingredient