Question

In the same group with the increase in atomic number the values of electron gain enthalpies are found to be less negative? Why?

Answer 1

Answer:

Explanation:

The size of the atom becomes lower as we move over a period, but the nuclear charge of the nucleus rises, owing to protons being added as we move over a period. The nucleus therefore readily draws the outer electron. the one we try to gain. Thus as we move across a period, the electron gain enthalpy becomes more and more negative, which also means that It requires less and less energy.

It's vice versa when the group is moved down as in that event the atomic size rises by a considerable quantity and the screening effect is bigger.  In this situation, atoms with full or half-filled orbitals are also an exception as half-filled or full orbitals are there, they are quite stable and do not ask for an extra electron.