Question 4
Within any period, which group holds the element with the lowest first ionization energy?
The right answer is the one marked above.
Group I. In period 3, sodium is 495 kJ mol−1; in period 2, lithium is 519 — the lowest figure in each row.
Group VIII is the opposite end: argon is 1521 and neon 2080, the highest in their periods. The group I metals give up an electron most readily of all, which is exactly why they are so reactive.