4. When the sulfide ion is oxidised to the sulfur atom, the number of 1 point
protons in the nucleus ... increase or decrease

increase

Explanation:

Oxidation, in chemistry, refers to when electrons are lost by an atom, hence, making the atom more positively charged. In contrast to this is reduction, which is the acceptance of electrons.

In this case, a sulfide ion (S²-) is said to be oxidized i.e loses electrons, till it becomes a sulfur atom (S). As the oxidation number has increased from -2 to 0, this means that the number of protons has INCREASED.