Question

Which of the following atoms will have the smallest size?

• A. $Mg$
• B. $Na$
• C. $Be$
• D. $Li$

Answer 1

The correct option is C $Be$

The atomic size decreases within a period from left to right, therefore $Li>Be$ and $Na>Mg$. The size increases in a group from top to bottom. Hence, the size of $Na$ is greater than $Li$. Overall order $Na>Mg>Li>Be$. Thus, $Be$ has smallest size.