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

Options

A. `Mg lt Ca lt C1 lt P `
B. `C1 lt P lt Mg lt Ca`
C. `P lt C1 lt Ca lt Mg`
D. `Ca lt Mg lt P lt C1`

Answer

B

Explanation

Arrange the elements : Ca, Mg, P and C1 in different groups and periods in increasing order fo their atomic numbers we have,
`{:("Group " to,,12,,15,,17),("Period " 2,,Mg,,P,,C1),("Period " 3 ,,Ca,,-,,-):}`
(i) Since atomic radii increase from top to bottom in a group therefore atomic radius of Ca is more than that of Mg i.e., `Mg lt Ca`
(ii) Since atomic radii decreases along a period from C1 decrease in the order : `Mg gt P gt C1` or increase in the order `: C1 lt P lt Mg`
Combining these two trends the atomic radii of `Ca, Mg, P ` and C1 increase in the order :
`C1 lt P lt Mg lt Ca` i.e., option ( b) is correct.