Question

What is the correct formula for the compound made by magnesium and nitrogen?

Answer 1

The correct formula for the Magnesium Nitrogen compound is `Mg_3N_2`.

Explanation:

Magnesium has two valence electrons, and Nitrogen has five valence electrons.

Answer 2

`Mg_3N_2`, magnesium nitride.

Explanation:

Magnesium is in Group 2, nitrogen is in Group 15; the formula is as you would predict from magnesium ion, `Mg^(2+)`, and nitride anion, `N^(3-)`. This is an ionic solid that hydrolyzes to give ammonia, and magnesium hydroxide, I.e.:

`Mg_3N_2` `+` `6H_2O rarr` `2NH_3` `+` `3Mg(OH)_2`

Answer 3

Magnesium and nitrogen combine to form magnesium nitride, `"Mg"_3"N"_2"`.

Explanation:

Magnesium nitride is an ionic compound. Magnesium forms ions with a `"2+"` charge, and nitrogen forms nitride ions with a `"3-"` charge. The overall charge of the compound must be zero. Therefore, the numerical value of the positive and negative charge must be `"6"`.

`3["Mg"]^(2+) + 2 ["N"]^(3-)` `rarr` `"Mg"_3"N"_2"`

`3xx(2+)=6+` and `2xx(3-)=6-`

`(6+)+(6-)=0`

An easy way to determine the formula unit of an ionic compound is called the crisscross method, as demonstrated in the video below.