Question

The atomic symbols of some elements are given below: $Si,C,Al,S,F,B,Li,Mg,O$ The number of elements from the above having atomic radius smaller than $Cl$ is________.

Answer 1

Answer: 5

Elements $Si,Al,S,Mg$ and $Cl$ belong to period
$3$ . The atomic radius decreases moving left to the right in a period. Hence, $Si,Al,S$ and $Mg$ will have greater radius than $Cl$ . The elements $C,F,B,Li$ and $O$ belong to period $2$ . Atomic radii of period $2$ elements are smaller than atomic radii
of period $3$ elements. Therefore, they have smaller radius than $Cl$ .