Question

Which of the following cation does not exist?

• A. ${{\mathrm{NH}}_4}^{+}$
• B. ${\mathrm{H}}^{+}$
• C. ${{\mathrm{ScO}}_2}^{+}$
• D. ${\mathrm{H}}_3{\mathrm{O}}^{+}$

Answer 1

The correct option is C

${{\mathrm{ScO}}_2}^{+}$

Explanation for correct option:

C. ${{\mathrm{ScO}}_2}^{+}$

Cation:

• Cation is a positively charged species.
• When an atom loses its electrons, it leads to the formation of an ion, which is known as a cation.
• A cation is smaller in size because the nucleus holds the electrons more tightly, resulting in a smaller atomic size.
• $\mathrm{Sc}$ is a metal with an atomic number $21$. After losing $3$ electrons it can not stabilize two oxygen atoms.
• Thus, ${{\mathrm{ScO}}_2}^{+}$ is not a stable ion and it does not exist.

Explanation for incorrect options:

(A)${{\mathrm{NH}}_4}^{+}$

• The name of ${{\mathrm{NH}}_4}^{+}$is ammonium ion.
• Cations such as ammonium ion exist in nature.

(B)${\mathrm{H}}^{+}$

• The name of ${\mathrm{H}}^{+}$is hydrogen ion.
• Cations such as Hydrogen ions exist in nature.

(D)${\mathrm{H}}_3{\mathrm{O}}^{+}$

• The name of ${\mathrm{H}}_3{\mathrm{O}}^{+}$is hydronium ion.
• Cations such as hydronium ion exist in nature.
• Thus, options A, B, and D are incorrect.

Hence, the correct option is C i.e. ${{\mathrm{ScO}}_2}^{+}$ ion does not exist.