Question

Name the member of the alkali metal group which has the lowest electron affinity.

Answer 1

Alkali metal group-

It includes the six elements of Group 1 of the periodic table and these elements are Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr).

Electron affinities:

It is the energy released when a neutral gaseous isolated atom gains an electron to form a stable negative charged gaseous ion, which is called electron affinity (E.A.).

The trend of Electron affinity in the Periodic table:

• On moving from left to right in a period of the periodic table, the atomic size decreases, and the nuclear charge increases. Thus, the electron affinity increases.
• On moving down the group in the periodic table, the atomic size increases, and the nuclear charge decreases. Thus, the electron affinity decreases.
• Francium (Fr) being the largest in the Alkali metal group has the lowest electron affinity.

Conclusion: Hence, the member of the alkali metal group that has the lowest electron affinity is Francium (Fr).