Question

What is the valency of magnesium in $M{{g}_{3}}{{N}_{2}}$?

Answer 1

Valency is defined as the number of electrons present in the outermost shell or the number of electrons required to completely fill that shell. Magnesium belongs to group two and nitrogen belongs to group fifteen.

Complete step-by-step answer: Magnesium is defined as a chemical element having an atomic number $12$ . It is an alkaline earth metal. It is a grey white metal which has very low boiling point and low melting point.
Nitrogen is defined as a chemical element having an atomic number$7$. It is a colourless, odourless tasteless element that is present plenty on the earth.
The number of electrons present in the outermost shell is known as valence electrons. If we want to calculate the valency of an element, you must know this formula-
Valency of metal is the number of electrons present in the outermost shell.
Valency of a non metal is the eight minus number of electrons present in the outermost shell.
In $M{{g}_{3}}{{N}_{2}}$, the three molecules of magnesium react with two nitrogen and result in the formation of magnesium nitride. Hence, the valency of magnesium is two and the valency of nitrogen is three.

Therefore, the valency of magnesium is two.

Note: The valency is different from the oxidation number as the valency does not contain any sign. The valency of nitrogen is three but the oxidation number lies from $-3$ to $+5$ .
If the number is less than or equal to four then the valency is the number of electrons present in the outermost shell and if it is more than four then the valency is eight minus the number of electrons present in the outermost shell.