# Electronic configuration of period 3 element from its successive ionization energies

Given below are the first five successive ionization energies $$(\mathrm{IE})$$ in $$\pu{kJ mol-1}$$ of an element in period 3.

$$\begin{array}{ccccc} \hline \mathrm{IE_1} & \mathrm{IE_2} & \mathrm{IE_3} & \mathrm{IE_4} & \mathrm{IE_5} \\ \hline 801 & 2427 & 3659 & 25022 & 32822 \\ \hline \end{array}$$

Deduce the electronic configuration of the valence energy level of the element. Explain how you came to this answer.

I need clarification on this question. I have explained into using my own knowledge, therefore correct me if am wrong.

I believe that the element in period three would be Al, since there is a big jump from $$\pu{3659 kJ/mol}$$ to $$\pu{25022 kJ/mol}$$. For the first three electron $$\mathrm{(3s)^2(3p)^1}$$, they are all in the same energy level which is the third shell and that takes $$\pu{801 kJ/mol} + \pu{2427 kJ/mol} + \pu{3659 kJ/mol}$$ to remove them, after that we notice a big jump after the third ionization energy indicating the its entering a new level of energy which is the second energy level.

Yes, your reasoning is logical and makes sense, but the question must have a typo because those IE values are the exact match for boron B, an element from period 2 right above aluminium Al (data from [1, p. 10-204], converted from $$\pu{eV}$$ to $$\pu{kJ mol-1}$$):

$$\begin{array}{lccccc} \hline \text{Element} & \mathrm{IE_1} & \mathrm{IE_2} & \mathrm{IE_3} & \mathrm{IE_4} & \mathrm{IE_5} \\ \hline \ce{B} & 801 & 2427 & 3659 & 25022 & 32822 \\ \ce{Al} & 578 & 1816 & 2745 & 11580 & 14842 \\ \ce{Ga} & 580 & 1980 & 2965 & 6102 & 8299 \\ \ce{In} & 559 & 1821 & 2704 & 5210 & \\ \ce{Tl} & 589 & 1971 & 2878 & & \\ \hline \end{array}$$

Another hint that it's not aluminium is the absolute value of the jump in energy between $$\mathrm{IE_3}$$ and $$\mathrm{IE_4}$$, which is too high for latter group 13 elements. Probably the author meant group 13, not period 3, but that's just a speculation at this point.

### References

1. Haynes, W. M.; Lide, D. R.; Bruno, T. J. CRC Handbook of Chemistry and Physics: A Ready-Reference Book of Chemical and Physical Data.; 2017; Vol. 97. ISBN 978-1-4987-5429-3.

### Appendix

Source code for the plot, pgfplots:

\documentclass{standalone}
\usepackage{pgfplots}
\usepackage{siunitx}

\begin{document}

\begin{tikzpicture}
\begin{axis}[
title={Successive ionization energies of group 13 elements},
xmin=1, xmax=5,
ymin=0, ymax=35000,
xlabel = $i$,
ylabel = {$\mathrm{IE}_i$/\si{\kilo\joule\per\mole}},
minor tick num = 1,
mark = *,
grid,
legend cell align = {left},
legend pos = north west,
]

(1,801)
(2,2427)
(3,3659)
(4,25022)
(5,32822)
};

(1,578)
(2,1816)
(3,2745)
(4,11580)
(5,14842)
};

(1,580)
(2,1980)
(3,2965)
(4,6102)
(5,8299)
};

(1,559)
(2,1821)
(3,2704)
(4,5210)
};

(1,589)
(2,1971)
(3,2878)
};

magick convert -density 120 G13_ionization_energies.pdf -quality 100 G13_ionization_energies.png