Question

Based on position in the periodic table and electron configuration, arrange these elements in order of decreasing Ei1.

Answer 1

Answer:

Rb<K<Ga<As<Se<S

Explanation:

We must remember that first ionization energy decreases down the group and increases across the period.

First ionization energy decreases down the group because of the addition of more shells which increases the distance between the nucleus and the outermost electron. Hence, Rb has a lower ionization energy that K.

Across the period, increase in the size of the nuclear charge causes the pull of the nucleus on the outermost electrons to increase thereby increasing the ionization energy. Hence ionization energy increases across the period. For this reason, the ionization energy of Ga<As<Se as shown.