Question

The order of first ionization potential values of three elements ‘X’ , ‘Y’ and ‘Z’ is $\text{Y>Z>X}$. What could be the elements X, Y and Z?

• A. $\mathrm{Al},\mathrm{Si},\mathrm{P}$
• B. $\mathrm{C},\mathrm{N},\mathrm{O}$
• C. $\mathrm{N},\mathrm{O},\mathrm{F}$
• D. $\mathrm{S},\mathrm{Cl},\mathrm{Ar}$

Answer 1

The correct option is B

$\mathrm{C},\mathrm{N},\mathrm{O}$

Explanation for correct option: (b)

1. The enthalpy change associated with the removal of the most loosely bound electron from an isolated gaseous atom of that element in the ground state is known as ionization enthalpy.
2. Ionization enthalpy generally decreases down the group and increases along a period.
3. The first ionization potential of nitrogen is higher than carbon and oxygen due to its half-filled configuration$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^3$. which is a stable configuration.
4. The ionization energy of oxygen will be higher than carbon.
5. Hence the elements are carbon ($\mathrm{C}$), nitrogen ($\mathrm{N}$) and oxygen ($\mathrm{O}$).

Explanation for incorrect options:

a) Here ionization energy of phosphorous will be higher than Aluminium and Silicon. Hence the given order $\text{Y>Z>X}$ is not followed here.

c) Here because of the half-filled configuration of nitrogen it has high ionization energy than fluorine and oxygen.

d) Here the given order of ionization potential $\text{Y>Z>X}$ is not followed. Because of the stable noble gas configuration of argon, it has high ionization energy than Sulfur and Chlorine.

Conclusion: Hence option (b) is correct and the elements are ($\mathrm{C}$), nitrogen ($\mathrm{N}$) and oxygen ($\mathrm{O}$). .