Question

In period $3$ of the periodic table, the atoms with the largest atomic radius is located in the group :

• A. $1$
• B. $3$
• C. $13$
• D. $17$
• E. $18$

Answer 1

Answer: (A)

$1$

As the atomic number of elements in Period 3 (Atomic number 11-18) increases, the atomic radius decreases. The atom with the largest atomic radius is $Na$ which is located in the group $1$.
This is because, the effect of increasing proton number is greater than that of the increasing effective nuclear charge; therefore, there is a greater nuclear attraction. The valence electrons are held closer towards the nucleus of the atom. As a result, the atomic radius decreases.