Question

Identify the correct order of the size of the following. [CBSE AIPMT 2007]

• A. $C{a}^{2+}<K^{+}<Ar<S^{2-}<C{l}^{-}$
• B. $C{a}^{2+}<K^{+}<Ar<C{l}^{-}<S^{2-}$
• C. $Ar<C{a}^{2+}<K^{+}<C{l}^{-}<S^{2-}$
• D. $C{a}^{2+}<Ar<K^{+}<C{l}^{-}<S^{2-}$

Answer 1

The correct option is B

$C{a}^{2+}<K^{+}<Ar<C{l}^{-}<S^{2-}$

A cation has always the lesser ionic size than „ metal atom due to loss of electrons and an anion always the greater size than metal atom due to of electrons. The given species are isoelertror., species as they contain same number of electrons. For isoelectronic species ionic radii.
$\propto \frac{1}{atomicnumber}$.
Ion: $C{a}^{2+}{K}^{+}Ar{S}^{2}Cl$
Atomic number : 20 19 18 16 17
So, the correct order of size is as
$C{a}^{2+}<K^{+}<Ar<C{l}^{-}<S^{2-}$