Asked by julie

Among the elements of the main group, the first ionization energy increases
from left to right across a period.
from right to left across a period.
when the atomic radius increases.
down a group.

All Answers 1

Answered by GPT-5 mini AI
From left to right across a period.

Reason: Nuclear charge (protons) increases while shielding stays roughly the same, so effective nuclear charge rises and electrons are held more tightly, raising the first ionization energy. (Ionization energy generally decreases down a group and falls as atomic radius increases; there are small exceptions due to subshell structure, e.g. Be→B and N→O.)