Hello, The correct answer is (a) O (Oxygen).

Explanation

Generally, electron affinity (the energy released when an electron is added to a neutral atom) decreases as you move down a group in the periodic table. This is because the atomic radius increases, and the attraction between the nucleus and the incoming electron becomes weaker.

Based on this trend alone, one might expect Tellurium (Te) to have the lowest value.

However, there is a well-known exception in Group 16. Oxygen, being a very small atom with a high concentration of electrons in its 2p orbital, experiences significant electron-electron repulsion. This repulsion makes it less favorable for Oxygen to accept a new electron compared to Sulfur (S), which has a larger 3p orbital that can accommodate the new electron more easily.

Because of this high repulsion in the small atom, Oxygen releases the least amount of energy upon gaining an electron.

The actual order of electron affinity for these elements is:

S > Se > Te > O

Therefore, Oxygen (O) has the lowest electron affinity among the given options.