Question

Rank the ions in each of the following sets in order of decreasing size. (a) My Notes Ask Your 0 > K+ Na+ 0 0 This answer has not been graded yet. (b) OF O N3- 02- > OF O 13- OOO A This answer has not been graded yet. (c) O Se2- Rb+ Br > Rb+ > OOO Rb+ O O This answer has not been graded yet.

Answer 1

Sol :- Down the group of periodic table atomic or ionic radii increases as number of shell increases. Left to right of periodic table atomic or ionic radii decreases as effective nuclear charge increases.

For the Iso-electronic species (having same number of electrons) anion of larger charge will be greater in size than anion of smaller charge or its parents atom, because effective nuclear charge per electron decreases, therefore size increases. Similarly, cation of larger charge will be smaller in size than cation of smaller charge or its parents atom, becausse effective nuclear charge per electron increases therefore size decreases.

So, Correct decreasing order of size will be :

(a). Ans :-

K⁺ > Na⁺ > Li⁺ (Because, Down the group of periodic table atomic or ionic radii increases as number of shell increases)

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(b). Ans :-

N^3- > O^2- > F^- (Iso-electronic because each of them contains 10 electrons)

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(c). Ans :-

Se^2- > Br^- > Rb⁺ (Iso-electronic because each of them contains 36 electrons)