Question

The most electropositive element among the following is:

• A. Na
• B. Ca
• C. K
• D. Cs

Hint:

Electropositive character increases as you go down a group.

Answer 1

The Correct Option is D

Step 1: Electropositive character is the tendency of an atom to lose electrons and form a positive ion. It depends mainly on how loosely the outermost electron is held.

Step 2: Down a group, atomic size increases because new electron shells are added, so the outermost electron is further from the nucleus and held more loosely. Electropositive character increases as we move down a group.

Step 3: Na, K and Cs belong to Group 1. Among them, Cs lies in Period 6, well below Na in Period 3 and K in Period 4.

Step 4: Since Cs has the largest atomic radius among these, its lone outer electron is held the most weakly by the nucleus, so it loses that electron most easily. Ca, a Group 2 element, also holds its electrons more tightly than the Group 1 alkali metals since it must lose two electrons and has a higher effective nuclear charge.

Answer: Cs is the most electropositive element here, option D.