Given the three statements below, pick the best answer.
I. The Z_eff for the highest energy electron in Be is higher than the Z_eff for the highest energy electron for N.
II. The second ionization energy for Mg is greater than the first ionization energy of Na.
III. The species O^{2 -}, Ne, and Na are isoelectronic.

Question

Quizplus · Accepted Answer

II is true because the second ionization energy for Mg involves removing an electron from a stable, full s-orbital, which requires more energy than removing the first electron from Na, which is in a less stable, partially-filled s-orbital. I is false because the effective nuclear charge (Z_eff) for the highest energy electron in Be is actually lower than that for N, due to N having more protons and a higher nuclear charge. III is false because O^2- (with 10 electrons), Ne (with 10 electrons), and Na^+ (with 10 electrons) are isoelectronic, not O^-, Ne, and Na.

Given the Three Statements Below, Pick the Best Answer