Question

Which of the following configurations is associated with the biggest jump between 2nd and 3rd I.E.?

• A. $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^1$
• B. $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^2$
• C. $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^1$
• D. $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^2$

Answer 1

The correct option is D

$1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^2$

The explanation for the correct answer

(D) $\mathbf{1}{\mathbf{s}}^{\mathbf{2}}\mathbf{2}{\mathbf{s}}^{\mathbf{2}}\mathbf{2}{\mathbf{p}}^{\mathbf{6}}\mathbf{3}{\mathbf{s}}^{\mathbf{2}}$

• Ionization energy is the energy required to remove the most loosely bonded electron from an isolated atom or ion.
• To have the highest jump in energy between 2nd and 3rd ionization energy, the second Ionization should be very low, and the third should be very high.
• 3rd I.E energy is the energy required to remove the 3rd last electron and 2nd ionization energy is the energy required to remove 2nd last electron.
• Here the third last electron is the last electron in $2{\mathrm{p}}^6$. This is a completely filled orbital and most stable system. So to remove the last electron from $2{\mathrm{p}}^6$the energy will be very high.
• The 2nd last electron is the 1st electron in $3{\mathrm{s}}^2$. By removing this electron it will get a stable configuration $2{\mathrm{p}}^6$. Thus energy to remove 2nd last electron will be very low.
• Therefore there will be a high jump between 2nd and 3rd I.E.
• Hence option D is correct.

The explanation for the incorrect answers

(A) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^1$

• Here removing 2nd last electron is difficult since $2{\mathrm{s}}^2$is completely filled. But not that much as that of from a p orbital since p orbital has high energy than the s orbital.
• Removing the third last electron will be easy since after removing 3rd last electron it will attain a completely filled configuration $1{\mathrm{s}}^2$.
• Even if there is a much gap between 2nd and 3rd I.E. The level is not that much of that of $\mathbf{1}{\mathbf{s}}^{\mathbf{2}}\mathbf{2}{\mathbf{s}}^{\mathbf{2}}\mathbf{2}{\mathbf{p}}^{\mathbf{6}}\mathbf{3}{\mathbf{s}}^{\mathbf{2}}$.
• Hence option A is incorrect.

(B) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^2$

• Removing 2nd last electron will be easy here since it attains a stable configuration$2{\mathrm{s}}^2$after removing two electrons.
• Removing 3rd electron here is not that easy since we are disturbing a completely filled orbital $2{\mathrm{s}}^2$.
• Here also there will be a sufficient gap between 2nd and 3rd I.E. But not that much of option D since that is between $2\mathrm{p}$ and $3\mathrm{p}$.
• Hence option B is incorrect.

(C) $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^1$

• Here removing 2nd last electron is difficult since we are disturbing a completely filled stable configuration $2{\mathrm{p}}^6$.
• But removing 3rd last electron doesn't make much difference here since we are not removing it from a completely filled orbital, also we are not getting a stable configuration after removing 3 electrons.
• Hence option c is also incorrect.

Therefore the correct answer is option (D) $\mathbf{1}{\mathbf{s}}^{\mathbf{2}}\mathbf{2}{\mathbf{s}}^{\mathbf{2}}\mathbf{2}{\mathbf{p}}^{\mathbf{6}}\mathbf{3}{\mathbf{s}}^{\mathbf{2}}$