Question

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

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

Answer 1

Answer: (A)

Isoelectronic means the species must have the same electronic configuration.
$\rightarrow$ Only the set of $K ^{+}, Ca ^{2+}, Sc ^{3+}, Cl ^{-}$represents isoelectronic species.
$K,\, Z =19$, Number of electrons in $K ^{+}=18$
$Ca,\, Z =20$, Number of electrons in $Ca ^{2+}=18$
$Sc,\, Z =21$, Number of electrons in $Sc ^{3+}=18$
$Cl,\, Z =17$, Number of electrons in $Cl ^{-}=18$