The predicted order of first ionization energies from highest to lowest for gallium (Ga), germanium (Ge), selenium (Se), and arsenic (As) is
Se As Ge Ga.
Ga Ge Se As.
Ga Ge As Se.
As Se Ge Ga.

Question

The predicted order of first ionization energies from highest to lowest for gallium (Ga), germanium (Ge), selenium (Se), and arsenic (As) is
Se > As > Ge > Ga.
Ga > Ge > Se > As.
Ga > Ge > As > Se.
As > Se > Ge > Ga.

aaronq · Answer

The order has to do with their position on the periodic table.

The ionization energy (IE) increases up any column (group) and increases to the right on any row (horizontal).