Electron affinity refers to the energy associated with: a. the removal of an electron from an atom in the gaseous state b. the removal of an electron from an atom in the solid state c. the addition of an electron to an atom in the gaseous state d. the addition of an electron to an atom in the solid state

Option (c) is the correct answer.

Explanation:

When an electron is added to a neutral atom to convert it into a negative ion then the amount of change taking place in its energy is known as electron affinity.

Smaller is the size of an atom more readily an electron will be gained by it because of strong force of attraction exerted by its nucleus towards the electron. As a result, lower will be the value of its electron affinity.

But when we move down a group then due to increase in shielding of nucleus by the electrons there will be less or no force of attraction exerted by the nucleus of an atom when an electron is added to it.

Thus, we can conclude that electron affinity refers to the energy associated with the addition of an electron to an atom in the gaseous state.