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#### Among the elements Ca, Mg, P and Cl, the order of increasing atomic radii is: Option 1) Ca < Mg < P < Cl Option 2) Mg < Ca < Cl < P Option 3) Cl < P < Mg < Ca Option 4) 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