Write the number of pairs in which size of first element or ion is higher as compare to II nd out of following nine pairs. ( B a a q 2 + , B e a q 2 + ), ( A l a q 3 + , B e a q 2 + ), ( Kr ,

Question

Write the number of pairs in which size of first element or ion is higher as compare to II $^{nd}$ out of following nine pairs.

( $B a_{a q}^{2 +}$ , $B e_{a q}^{2 +}$ ), ( $A l_{a q}^{3 +}$ , $B e_{a q}^{2 +}$ ), ( $Kr$ , $N e$ ), ( $N a$ , $N a^{+}$ ), ( $Cl$ , $C l^{-}$ ), ( $I^{-}$ , $C l^{-}$ ), ( $L i_{a q}^{+}$ , $N a_{a q}^{+}$ ), ( $L i$ , $N a$ ), ( $L i^{+}$ , $N a^{+}$ ).

TestHub · Accepted Answer

Concepts: Cation < atom, Anion > atom, size increases down group, hydrated size inverse to ionic size.

Ba²⁺(aq) > Be²⁺(aq) (down group ↑ size)

Kr > Ne (down group ↑ size)

Na > Na⁺ (cation smaller)

I⁻ > Cl⁻ (down group ↑ size)

(Al³⁺(aq) > Be²⁺(aq)) (IMPORTANT)
Although Al³⁺ has higher charge, Be²⁺ is very small → highly hydrated → becomes effectively smaller

Chemistry - PERIODIC TABLE Question with Solution | TestHub

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JEE Advanced (2028)