Question

Why the ionization energy decrease down the group?

Answer 1

Explanation:

As we go down the group the atomic size increase and shielding effect slightly decreases and thus it becomes easy for outermost electron to leave the atom and thus it is less down the group

Answer 2

Explanation:

ionization energy increases across a period and decreases down a group. Across a period, effective nuclear charge increases as electron shielding remains constant.

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