Question

Which one of the following sets of ions represents the collection of isoelectronic species ?

• A. $K^+, Cl^- , Mg^{2+}, Sc^{3+}$
• B. $Na^+ , Ca^{2+}, Sc^{3+}, F^-$
• C. $K^+,Ca^{2+},Sc^{3+},Cl^-$
• D. $Na^+,Mg^{2+},Al^{3+},Cl^-$

Answer 1

Answer: (C)

$K^+,Ca^{2+},Sc^{3+},Cl^-$

Answer 2

The number of electrons in these species are

Ions
Number of electrons

$Na ^{+}$
$11 -1 = 10$
$Mg ^{2+}$
$12 -2= 10$
$Al ^{3+}$
$13 - 3 = 13$
$F ^{-}$
$9 + 1 = 10$
$K ^{+}$
$19 + 1 = 10$
$Ca ^{2+}$
$20 + 2 = 18$
$Sc ^{3+}$
$21 + 3 = 18$
$Cl ^{-}$
$17 + 1 = 18$
$\therefore Na ^{+}, Mg ^{2+}, Al ^{3+}$ and $F ^{-}$ are isoelectronic species and each one of which has $10 . Also , K ^{+}, Ca ^{2+}, Sc ^{3+}$ and $Cl ^{-}$ are electronic species and each one of which has 18 electrons.