Question

An element in period 3 whose electron affinity is zero is:

• A. Sulphur
• B. Sodium
• C. Chlorine
• D. Argon

Answer 1

The correct option is D Argon

Electron affinity is defined as the change in energy (in kJ/mole) of a neutral atom (in the gaseous phase) when an electron is added to the atom to form a negative ion.In other words, the neutral atom's likelihood of gaining an electron.
Argon has $n{s}^2{p}^6$ configuration, an octet is complete so it does not have any tendency to gain an electron and they have zero electron affinity.