Structure of Atom - Result Question 46
####50. The ions $O^{2-}, F^{-}, Na^{+}, Mg^{2+}$ and $Al^{3+}$ are isoelectronic. Their ionic radii show [2003]
(a) A decrease from $O^{2-}$ to $F^{-}$and then increase from $Na^{+}$to $Al^{3+}$
(b) A significant increase from $O^{2-}$ to $Al^{3+}$
(c) A significant decrease from $O^{2-}$ to $Al^{3+}$
(d) An increase from $O^{2-}$ to $F^{-}$and then decrease from $Na^{+}$to $Al^{3+}$
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Solution:
- (c) Amongst isoelectronic species, ionic radii of anion is more than that of cations. Further size of anion increases with increase in -ve charge and size of cation decreases with increase in + ve charge. Hence, ionic radii decreases from $O^{-}$to $Al^{3+}$.
