Q34 / 180 · COMEDK 2022 · Chemistry
$\text{O}^{2-}$, $\text{F}^-$, $\text{Mg}^{2+}$, $\text{Al}^{3+}$, $\text{O}_2$, $\text{F}_2$. How many of the species given above are isoelectronic?
- Correct answerA4
- B2
- C3
- D5
Solution
Isoelectronic species have the same number of electrons.
$O^{2-}$: $8 + 2 = 10$ electrons
$F^-$: $9 + 1 = 10$ electrons
$Mg^{2+}$: $12 - 2 = 10$ electrons
$Al^{3+}$: $13 - 3 = 10$ electrons
$O_2$: $2 \times 8 = 16$ electrons
$F_2$: $2 \times 9 = 18$ electrons
$O^{2-}$, $F^-$, $Mg^{2+}$, and $Al^{3+}$ all have 10 electrons. Thus 4 species are isoelectronic.
$O^{2-}$: $8 + 2 = 10$ electrons
$F^-$: $9 + 1 = 10$ electrons
$Mg^{2+}$: $12 - 2 = 10$ electrons
$Al^{3+}$: $13 - 3 = 10$ electrons
$O_2$: $2 \times 8 = 16$ electrons
$F_2$: $2 \times 9 = 18$ electrons
$O^{2-}$, $F^-$, $Mg^{2+}$, and $Al^{3+}$ all have 10 electrons. Thus 4 species are isoelectronic.
Hence, the correct answer is option: 'A'.