Question

What is the name and formula for the compound formed from magnesium, 2+, and phosphide, 3-, ions?

Answer 1

`"Magnesium phosphide........."`

Explanation:

And to form the salt, we draft in anions and cations to form a neutral entity, i.e. here `Mg_3P_2`........This would be nasty stuff; so if you have an old, unopened bottles lurking in the back of a cupboard exercise due care. Of course, an opened bottle might have hydrolyzed long ago....

So how did I know the formula was `Mg_3P_2`? Well, the constituent ions are `Mg^(2+)` and phosphide, `P^(3-)`. The salt MUST be electrically neutral, so we cross mulitply to give `2xxP^(3-)+3xxMg^(2+)=Mg_3P_2`. Capisce?