Question

Which of the following is the correct order in terms of covalent radius?

• A.
• B.
• C.
• D. None of these

Answer 1

The correct option is C

Now, Lets try to recall the periodic trends in terms of atomic radius.

Along a period from Left to Right, Atomic Radius decreases because effective nuclear charge increases on the valance electrons resulting in the increased attraction of electrons to the nucleus.

Down the group from Top to Bottom, Atomic Radius increases because the principal quantum number (n) increases and the valance electrons are farther from the nucleus.

Now, $Li$ and $Be$ belongs to second period.

$\Rightarrow$ $Li>Be$ [Atomic radius decreases along the period]

Between, $Li$ and $Mg$

$\Rightarrow$ $Mg>Li$ [Atomic radius decreases down the group]

Between, $Na$ and $Mg$

$\Rightarrow$ $Na>Mg$

Therefore, the correct order will be

$Na>Mg>Li>Be$.