Question

Which among the following elements has the largest atomic radii

• A. $Na$
• B. $Mg$
• C. $K$
• D. $Ca$

Answer 1

The correct option is C

$K$

Explanation for the correct option:

Because size is increases down the group due to increase in outer shells and size decreases left to right in period due to many factors like Z_eff, increasing no. of protons etc. In options we have $Na,Mg,K$and $Ca.$

$Na$ and$K$ are of same group and $Mg$ and $Ca$ are of same group.

So the correct option is b)$K$, it has the largest atomic radii among four of them.

Explanation for the incorrect options:

A) $Na$: Sodium $\left(Na\right)$ has larger atomic radii than Magnesium $\left(Mg\right).$

B) $Mg$: Magnesium $\left(Mg\right)$ has larger atomic radii than other group members which lies before magnesium and other period elements which lie after $Mg$.

D)$Ca$: Calcium has larger atomic radii than Magnesium $\left(Mg\right).$.

Option (A), (B) and (D) are incorrect.

Hence option (C) is correct. $K$ has largest atomic radii than other given elements.