Question

Ionization energy of sodium is ______ than that of potassium.

• A. more
• B. less

Answer 1

Step-1:

The energy needed to take an electron from the outer shell of isolated atom is ionization energy. It is denoted as IE. The atomic size, effective nuclear charge and screening effect are the factors that influence the ionization energy.

Step-2:

Trend of ionization energy across a period: On moving from left to right across the period, the ionization energy increases. This is due to the decrease in size of atom on increasing the atomic number and thus, the electrons in valence shell goes closer to the nucleus. There is more energy needed to remove an electron from outermost shell.

Trend of ionization energy down the group: The ionization energy decreases down the group because of the increase in number of valence shells.

Step-3:

Sodium ($\mathrm{Na}$) and Potassium ($\mathrm{K}$) belongs to same group 1. The ionization energy of Sodium ($\mathrm{Na}$) is more than that of Potassium ($\mathrm{K}$) because the distance of the outermost shell (N-shell) from the nucleus of Potassium is larger than that of Sodium.

Final answer:

Ionization energy of Sodium is more than that of Potassium.