Question

Which of the following is not isoelectronic with $O^{-2}$?

• A. $N^{-3}$
• B. $N{a}^{+}$
• C. $F^{-}$
• D. $T{i}^{+}$

Answer 1

The correct option is D

$T{i}^{+}$

D)

An explanation for the correct option,

1. Isoelectronic species are those ions or atoms that have the same number of electrons.
2. Oxygen here has the atomic number of 8, which means it has 8 protons and 8 electrons.
3. The charge here is negative $(-2)$, which means that the given atom has accepted two electrons to form an anion.
4. So the total number of electrons $O^{-2}$ has is, $8+2=10$ electrons.
5. Now Titanium has the atomic number of 22, which means it has 22 protons and 22 electrons. The positive one $(+1)$ charge means it has lost one electron to form a cation.
6. Total number of electrons for $T{i}^{+}$=$22-1=21.$
7. This means $T{i}^{+}$ is not isoelectronic with O-2. Hence option (D) is the correct option.

An explanation for the incorrect option

1. A) Total number of electrons $N^{-3}$ has $7+3=10$electrons, option (A) is incorrect.
2. B) Total number of electrons $N{a}^{+}$ has$11-1=10$ electrons, option (B) is incorrect.
3. C) Total number of electrons $F^{-}$ has $9+1=10$electrons. Option (C) is incorrect.

Hence option (D) is correct, as the specie is not isoelectronic with $T{i}^{+}$, and options (A), (B), and (C) are incorrect.