Question

Write the following isoelectronic ions on the basis of their increasing order of the size (¡) F-
(¡¡) Al+++
(¡¡¡) Na+ (4) N3-

Answer 1

The increasing order of the size of the isoelectronic ions are

$Al^{+++}$>$Na^{+}$>$F^{-}$>$N^{3-}$

• Isoelectronic species are defined as the species which has the same number of electrons in their valence shell.
• The size of isoelectronic species tends to decreases as the charge inside the nucleus of any species increases.
• The species  $F^{-}$ , $Al^{+++}$, $Na^{+}$ and $N^{3-}$ has the same number of electrons in the valence shell.
• But the nuclear charge present in each of the species is different.
• The nuclear charge in the species are: $Al^{+++}$ = 13, $Na^{+}$ = 11,$F^{-}$=9, $N^{3-}$=7
• The species which has greater nuclear charge among all the species is $Al^{+++}$ followed by $Na^{+}$ , $F^{-}$ and then $N^{3-}$
• Hence, the order of increasing size is as follow:                                   $Al^{+++}$>$Na^{+}$>$F^{-}$>$N^{3-}$