Question

How many electrons does nitrogen have to gain when it becomes an ion?

Answer 1

The atomic number of nitrogen is 7 so the electronic configuration is $[He]2{s^2}2{p^3}$. Total 5 valence electrons are present in the outermost shell. The element gains or loses electrons to complete its octet of 8 electrons.

Complete step by step answer:
Nitrogen is the chemical element present in the periodic table in group 15 and period 2. It is a p-block element. The nitrogen is represented by the symbol N. The atomic number of nitrogen is 7. The electronic configuration of nitrogen is $[He]2{s^2}2{p^3}$. The valence electrons present in nitrogen is 5. The valence electrons are defined as those electrons which are present in the outermost shell of the electronic configuration and take part in the chemical bonding.
Any element can gain electrons from its neighboring element or lose electrons to complete their octet. When the element loses or gains electrons it forms an ion. When the element gains electrons it forms anion with negatively charged electrons. When the element loses electrons it forms a cation with a positive charge.
As the nitrogen element contains 5 valence electrons in the outermost shell, it needs 3 more electrons to complete its octet of 8 electrons. So 3 electrons are gained by nitrogen to form anion with -3 charge. So the resulting anion is ${N^{3 - }}$.
Therefore, nitrogen needs 3 electrons to become an ion.

Note:
The nitrogen can lose its three electrons from the valence shell to become a cation with +3 charge. The resulting cation formed is ${N^{3 + }}$.