Among the elements Ca, Mg, P and Cl, the order of increasing atomic radii is

29 2010 AIPMT-MAINS Classification of Elements and Periodicity in PropertiesAtomic radius Easy
Among the elements Ca, Mg, P and Cl, the order of increasing atomic radii is
A Mg < Ca < Cl < P
B Cl < P < Mg < Ca
C P < Cl < Ca < Mg
D Ca < Mg < P < Cl

Detailed Solution

Mg, P and Cl belong to the third period. Across a period the nuclear charge increases while electrons enter the same shell, so the atomic radius decreases from left to right: Mg > P > Cl.
Ca lies just below Mg in group 2. Down a group a new shell is added, so the radius increases: Ca > Mg.
Atomic radii (pm): Cl = 99, P = 110, Mg = 160, Ca = 197.
Increasing order of atomic radii: Cl < P < Mg < Ca

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