Question

Why does the ionization enthalpy
gradually decreases in a group?​

Answer 1

Answer:

ionisation enthalpy decreases with an increase in atomic size

Answer 2

Answer:

Conversely, as one progresses down a group on the periodic table, the ionization energy will likely decrease since the valence electrons are farther away from the nucleus and experience greater shielding. They experience a weaker attraction to the positive charge of the nucleus.

Explanation:

Ionization enthalpy gradually decreases in group because the nuclear charge on valence electron decreases on moving down a group, hence, the electrons are held loosely and also atomic size increases down a group.

It can also be explained as = (Nucleus exerts weak force on outermost electrons and minimum amount of energy is required to remove an electron. So ionization energy will decrease down a group)

Hope it helps..... ≧ω≦