Question

How does a sulphur $-2$ ion differ from a neutral sulphur atom?

Answer 1

The species which have positive or negative charge as a whole because of gain or loss of electrons from their neutral selves, are termed as ions.
The negative ions are formed because of the gain of electrons, because the electrons are negatively charged species, while, positive charge is obtained because of the loss of electrons, for the same reason.
The species which have positive or negative charge as a whole because of gain or loss of electrons from their neutral selves, are termed as ions.
The negative ions are formed because of the gain of electrons, because the electrons are negatively charged species, while, positive charge is obtained because of the loss of electrons, for the same reason.

Complete answer:
In order to understand this question, we must first look at the electronic configuration of the sulphur atom, which is $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{4}}$. As we can see that the outermost orbitals contain six electrons. We know that an atom attains stability when it has eight electrons in its outermost orbital, and the atoms adjust it by loss or gain of electrons from the outermost orbital and consequently acquires a positive or negative charge.
In the case of sulphur atoms, the outermost orbitals need two more electrons in order to attain a stable octet configuration. So, it gains two electrons which results in formation of a negatively charged ion, also called anion. This phenomena can be expressed in the form of an equation,
$S+2{{e}^{-}}\to {{S}^{2-}}$
Where, $S$ is the atomic symbol of the atom sulphur. Now, as we can see, the sulphur atom before it gains two electrons, is neutral in charge. It cannot form ionic bonds with other ionic species while it is neutral, whereas in case of the anionic sulphur, it has the ability to form ionic bonds with positive cations.

Note: The cations or anions differ from the neutral atoms in terms of charge and electronegativity, as well as the attractions towards opposite charge.
The electronegativity of the neutral atoms having more than four or five electrons in its outermost orbitals, would be more than the electronegativity of negative atoms.