Question

select the correct statement(s) about ionization energy. it decreases as you move down a group. ionization energy from highest to lowest is potassium (k), magnesium (mg), krypton (kr), and helium (he). ionization energy from highest to lowest is helium (he), krypton (kr), magnesium (mg), and potassium (k). it increases as you move across a period. it increases as you move down a group. it decreases as you move across a period.

Explanation:

• For the trend down a group: As you move down a group in the periodic table, the atomic radius increases. The outermost electrons are further from the nucleus and are shielded by more inner - electron shells. So, less energy is required to remove an electron (ionization energy decreases).
• For the trend across a period: As you move across a period (from left to right), the nuclear charge increases while the electron - shielding effect remains relatively constant. The electrons are more tightly bound to the nucleus, so more energy is required to remove an electron (ionization energy increases).
• For the order of ionization energy: Helium (\(He\)) is in the first period (noble gas), has a very high ionization energy. Krypton (\(Kr\)) is a noble gas in the fourth period. Magnesium (\(Mg\)) is in the third period (Group 2), and potassium (\(K\)) is in the fourth period (Group 1). Since ionization energy decreases down a group and increases across a period (for main - group elements), the order of ionization energy from highest to lowest is \(He> Kr>Mg > K\).

Answer:

• It decreases as you move down a group.
• Ionization energy from highest to lowest is helium (\(He\)), krypton (\(Kr\)), magnesium (\(Mg\)), and potassium (\(K\)).
• It increases as you move across a period.