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Which of the following order of radii is correct?
A. `Li lt Be lt Mg`
B. `H^(+) lt Li^(+) lt H^(-)`
C. `O lt F lt Ne`
D. `Li lt Na lt K lt Ca lt Rb`

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1 Answers

Correct Answer - B
Atomic radius increases on moving top of bottom in a group due to increasing number of shells. However, it decreasing on moving left to right in a period due to increasing `Z_(eff)` and addition of electrons to the saem shell. For `H`, cation is smaller than parent atom while anion is bigger than parent atom. `H^(-)` and `Li^(+)` are isoelectronic species. So, ionic size `prop (1)/("nuclear charge")`. Hence the correct order is `H^(+) lt Li^(+) lt H^(-)`.

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