Verified Answer :

An anion.   

These group of atoms because they are negatively charged migrate to the anode (positive terminal) of an electrolytic process.

Answer: Option (a) is the correct answer.

Explanation:

When electrons are removed from a neutral atom or ion then the atom attains a positive charge. Therefore, it is called a cation.

For example, \(Na^{+}\) is a cation.

Whereas when electrons are added to a neutral atom or ion the then the atom attains a negative charge. Therefore, it is called an anion.

For example, \(Cl^{-}\) is an anion.

Anode is a positively charged electrode and cathode is a negatively charged electrode.

Thus, we can conclude that a negatively charged atom or group of atoms is called an anion.