Question

# The nitride ion consists of:[A] 7 protons + 10 electrons[B] 10 protons + 10 electrons[C] 7 protons + 7 electrons[D] 10 protons + 7 electrons

We know that the atomic number of nitrogen is 7, which means in neutral state it has 7 electrons and 7 protons. But when it gains three electrons, which we can write as-$N+3{{e}^{-}}\to {{N}^{3-}}$, it becomes ${{N}^{3-}}$.
Note: The charge of a particle depends upon the number of electrons in it but the number of protons in an atom is always the same. However, the number of neutrons is not always equal to the number of protons. Atoms of the same elements can have different numbers of neutrons but the same number of protons. Such elements are called isotopes. For example, hydrogen has three isotopes-${}_{1}^{1}H$ (hydrogen) has no neutron,${}_{1}^{2}H$(deuterium) has one neutron and${}_{1}^{3}H$(tritium) has two neutrons.