Among the elements Ca, Mg, P and Cl, the order of increasing atomic radii is:
Ca < Mg < P < Cl
Mg < Ca < Cl < P
Cl < P < Mg < Ca
P < Cl < Ca < Mg
As learnt in
Periodicity of atomic radius and ionic radius in period -
In a period from left to right the effective nuclear charge increases because the next electron fills in the same shell. So the atomic size decrease.
- wherein
and
Size of atom and ion in a group -
In a group moving from top to the bottom the number of shell increases.So the atomic size increases.
- wherein
In a period from left to right, the effective nuclear charge increases as the electrons fill the same shell and thus, the atomic size decreases. Whereas, in a group, moving from top to bottom, the number of shells increase thereby increasing the atomic radius.
Therefore, the order of increasing atomic radii is:
Cl < P < Mg < Ca
Option 1)
Ca < Mg < P < Cl
This option is incorrect
Option 2)
Mg < Ca < Cl < P
This option is incorrect
Option 3)
Cl < P < Mg < Ca
This option is correct
Option 4)
P < Cl < Ca < Mg
This option is incorrect