Question

Among of alkali metals, the metal with highest ionization potential is :

• A. Li
• B. Na
• C. K
• D. Rb

Answer 1

Answer: (A)

Li

Alkali metals have the lowest ionization energy in each period. Within the group, as we go down, the ionization energies of alkali metals decrease due to their atomic size being the largest in their respective periods.

In large atoms the valence electrons are loosely held by the nucleus and are easily lost, leading them to have low ionization energies and acquiring stable noble gas configurations.

On moving down the group, the atomic size increases and the number of inner shells also increases, increasing the magnitude of screening effect and consequently, the ionization energy decreases down the group. Hence Lithium will have the highest first ionization potential out of the alkali metals.