Question

The elctron affinity value of be,mg and noble gas is zero and those of n

Answer 1

Affinity is the change in energy of the atom when an electron is added.

Electron affinity of Be and Mg are almost zero but they are not equal to zero.

Be and Mg have filled sub shells. They are much more stable than if they had an extra electron.

Now, the noble gas have complete valence electron shells. They have a complete set of 8 electrons. Since the Noble Gases already have complete octet, they have an affinity of 0.