Sodium lies on the left-hand side of the period, while phosphorus lies in the right-hand side of the same period. Along a period, atomic radius decreases as the nuclear force of attraction increases. Then too, Sodium has a largest atomic radius in the period after Argon.Īlso, sodium and phosphorus lie in the same period. It isn’t fair to compare these with a van der Waals radius though.

It is fair to compare metallic and covalent radii because they both are both being measured in tightly bonded circumstances. Van der Waals radius- Ar as it does not form any strong bond. In the zeroth group the atom gets stabilised due to the complete octet in the outermost shell due to which effective nuclear charge becomes lesser than the effective nuclear charge of chlorine which makes argon atom bigger than chlorine.īut still the effective nuclear charge is greater than that of sodium due to which the size of the argon atom is smaller than that of the sodium atom. But this is applicable only till halogen groups. Thus, while moving in a period from left to right the atomic size decreases as the effective nuclear charge increases. The outer or valence electrons pull closer towards the nucleus as the positive charge in the nucleus increases resulting in the decreasing in the atomic radius across the period. third period.Īs we move across the period, electrons are added to the same shell at the same distance from the nucleus of the atom. Sodium and Argon are the elements of the same period i.e. Thus,Ītomic radius along the period- Decreases from left to right.Ītomic radius along the group- Increases from top to bottom. Use the hint that atomic radius gradually increases as you go down the group.įirstly, we shall be thorough with the periodicity trends of the modern periodic table to answer the given question. Thus, the trend will give the proper explanation for the variations with respect to sodium. Hint: The statements are based on the periodicity trends of the periodic table.

Ar atomic radius