Question

A nitride ion has $7$ protons, $8$ neutrons and $10$ electrons. What is the overall charge on this ion?

Answer 1

Hint: The net charge of any ion is given by the balance which exists between the number of electrons that surround the nucleus and the number of protons present in the nucleus. If a neutral atom gains electrons, an anion is formed and if a neutral atom loses electrons, a cation is formed.

Complete answer:
The nitride ion has $7$ protons in its nucleus and $10$ electrons surrounding its nucleus. The neutral would have contained $7$ protons and $7$ electrons. Note that the neutral atom gained three electrons to form the negatively charged ion i.e. anion. The magnitude of the negative charge is the difference between the number of protons and the number of electrons. It means, each extra electron will add a charge of $1$ to the ion. Here, the difference between the number of protons and the number of electrons is three. These three electrons will add a charge of three to the ion. The overall charge on the nitride anion will be $3 - $ and the nitride ion is represented as ${N^{3 - }}$ .
Therefore, the overall charge on the nitride anion will be $3 - $ and the nitride ion is represented as ${N^{3 - }}$ .

Note:
Note that the number of neutrons do not play any role in the net charge of an atom. If an atom has an equal number of electrons and protons, its net charge will be equal to zero i.e. it is said to be a neutral atom.