Chapter 7, Problem 104A

Interpretation Introduction

Interpretation:

The given table needs to be completed.

Concept introduction:

Electron configuration shows that the orbitals that are occupied by electrons in an atom. Electron occupies orbitals to minimize the energy of the atom. So, lower energy level fills before higher energy orbitals. Each orbital can hold maximum of two electrons.

Answer to Problem 104A

Element	Valence electrons	Ion formed
Selenium	6	$-2,+4,+6$
Tin	4	$+2,+4$
Iodine	7	$-1$
Argon	8	n/a

Explanation of Solution

Electron configuration of selenium, tin, iodine and argon is as follows:

$\begin{array}{c}{\text{Se=1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^{\text{6}}{\text{3s}}^{\text{2}}{\text{3p}}^{\text{6}}{\text{4s}}^{\text{2}}{\text{3d}}^{\text{10}}{\text{4p}}^{\text{4}}\\ {\text{Sn=1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^{\text{6}}{\text{3s}}^{\text{2}}{\text{3p}}^{\text{6}}{\text{4s}}^{\text{2}}{\text{3d}}^{\text{10}}{\text{4p}}^{\text{6}}{\text{5s}}^{\text{2}}{\text{4d}}^{\text{10}}{\text{5p}}^{\text{2}}\\ {\text{I=1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^{\text{6}}{\text{3s}}^{\text{2}}{\text{3p}}^{\text{6}}{\text{4s}}^{\text{2}}{\text{3d}}^{\text{10}}{\text{4p}}^{\text{6}}{\text{5s}}^{\text{2}}{\text{4d}}^{\text{10}}{\text{5p}}^5\\ \text{Ar}={\text{1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^{\text{6}}{\text{3s}}^{\text{2}}{\text{3p}}^{\text{6}}\end{array}$

Now, determine the valence electrons for each element. Se has two valence electrons in the $\text{4s}$ subshell and four valence electrons in $\text{4p}$ subshell. Therefore, Se contains total six valence electrons. In Sn, the $\text{5s}$ orbital has 2 valence electrons and $\text{5p}$ has two valance electrons, total four valence electrons. In I, the $\text{5s}$ orbital has 2 valence electrons and $\text{5p}$ has 5 valance electrons, total seven valence electrons. Ar has 2 electrons in $\text{3s}$ subshell and 6 electrons in $\text{3p}$ subshell, a total of eight electrons.

Selenium can gain 2 electrons to have a full 4p orbital and becomes $-2$. It can lose 4 electrons to have an empty p orbital and become +4 or six electrons to become +6. Tin can lose 2 or 4 electrons to become +2 and +4. Iodine gains one electron to become $-1$ anion. Argon is a noble gas, it has total of eight electrons in the outermost shell. Therefore, it does not form ions.

Conclusion

Valence electrons are the outer shell electrons. They participate in the formation of chemical bond.