Chapter 2, Problem 99E

Valence electrons are those electrons in the outermost principal quantum level (highest n level) of an atom in its ground state. Groups lA to 8A have from 1 to 8 valence electrons. For each group of the representative elements (1A-8A). give the number of valence electrons, the general valence electron configuration, a sample element in that group, and the specific valence electron configuration for that element.

Interpretation Introduction

sInterpretation: The number of valence electrons, the general valence electron configuration, a sample element and the specific valence electron configuration of the sample element for Groups $1$ A to $8$ A are to be stated.

Concept introduction: Electronic configuration of an atom is defined as the distribution of electrons in atomic orbitals. It describes that each electron move independently in an orbital. Atomic orbital is defined as a space present around the nucleus of an atom where an electron is found. The number of electrons present in the outermost shell of an atom is known as valence electrons.

Answer to Problem 99E

The number of valence electrons, the general valence electron configuration, a sample element and the specific valence electron configuration of the sample element for Groups $1$ A to 8A are rightfully stated.

Explanation of Solution

Explanation

To determine: The number of valence electrons, the general valence electron configuration, a sample element and the specific valence electron configuration of the sample element for Groups $1$ A to $8$ A.

The number of valence electrons, the general valence electron configuration, a sample element and the specific valence electron configuration of the sample element for Group $\text{1A}$.

The number of valence electrons is the number of electrons present in the outermost shell of any element and they are equal to the atoms main group number. The Group $\text{1A}$ indicates that the outermost shell of all elements present in Group $\text{1A}$ have one electron. Hence, the number of valence electrons present in Group $\text{1A}$ is one.

The valence electron in $\text{1A}$ is present in $s$ orbital. The general valence electron configuration of Group $\text{1A}$ is $n{s}^1$.

The sample element for this group is Lithium $\left(\text{Li}\right)$ as it contains only one electron in its valence shell and therefore belongs to Group $\text{1A}$.

The atomic number of Lithium $\left(\text{Li}\right)$ is $3$ and according to Hund’s rules the ground state electronic configuration of Lithium $\left(\text{Li}\right)$ is $1s^{2}2s^1$ with one valence electron present in $2s$ orbital. Therefore, the valence electron configuration of Lithium $\left(\text{Li}\right)$ is $2s^1$.

Explanation

The number of valence electrons, the general valence electron configuration, a sample element and the specific valence electron configuration of the sample element for Group $2\text{A}$.

The Group $\text{2A}$ indicates that the outermost shell of all elements present in Group $\text{2A}$ have two electron. Hence, the number of valence electrons present in Group $\text{2A}$ is two.

The valence electron in $\text{2A}$ is present in $s$ orbital as it accommodates maximum of two electrons. The general valence electron configuration of Group $\text{2A}$ is $n{s}^2$.

The sample element for this group is Radium $\left(\text{Ra}\right)$ as it contains two electrons in its valence shell and therefore belongs to Group $\text{2A}$.

The atomic number of Radium $\left(\text{Ra}\right)$ is $88$ and according to Hund’s rules the ground state electronic configuration of Radium $\left(\text{Ra}\right)$ with preceding noble gas Radon becomes $\left[\text{Rn}\right]7s^2$ with two valence electrons present in $7s$ orbital. Therefore, the valence electron configuration of Radium $\left(\text{Ra}\right)$ is $7s^2$.

Explanation

The number of valence electrons, the general valence electron configuration, a sample element and the specific valence electron configuration of the sample element for Group $3\text{A}$.

The Group $\text{3A}$ indicates that the outermost shell of all elements present in Group $\text{3A}$ has three electrons. Hence, the number of valence electrons present in Group $\text{3A}$ is three.

The valence electron in $\text{3A}$ is also present in $p$ orbital after filling the $s$ orbital as it accommodates maximum of two electrons. The general valence electron configuration of Group $\text{3A}$ is $n{s}^{2}n{p}^1$.

The sample element for this group is Gallium $\left(\text{Ga}\right)$ as it contains three electrons in its valence shell and therefore belongs to Group $\text{3A}$.

The atomic number of Gallium $\left(\text{Ga}\right)$ is $31$ and according to Hund’s rules the ground state electronic configuration of Gallium $\left(\text{Ga}\right)$ with preceding noble gas Argon becomes $\left[\text{Ar}\right]4s^{2}3d^{10}4p^1$ with three valence electrons present in $4s\text{ and }4p$ orbitals. Therefore, the valence electron configuration of Gallium $\left(\text{Ga}\right)$ is $4s^{2}4p^1$.

Explanation

The number of valence electrons, the general valence electron configuration, a sample element and the specific valence electron configuration of the sample element for Group $\text{4A}$.

The Group $\text{4A}$ indicates that the outermost shell of all elements present in Group $\text{4A}$ has four electrons. Hence, the number of valence electrons present in Group $\text{4A}$ is four.

The valence electron in $\text{4A}$ is also present in $p$ orbital after filling the $s$ orbital as the $s$ orbital accommodates maximum of two electrons. The general valence electron configuration of Group $\text{4A}$ is $n{s}^{2}n{p}^2$.

The sample element for this group is Silicon $\left(\text{Si}\right)$ as it contains four electrons in its valence shell and therefore belongs to Group $\text{4A}$.

The atomic number of Silicon $\left(\text{Si}\right)$ is $14$ and according to Hund’s rules the ground state electronic configuration of Silicon $\left(\text{Si}\right)$ with preceding noble gas Neon becomes $\left[\text{Ne}\right]3s^{2}3p^2$ with four valence electrons present in $3s\text{ and 3}p$ orbitals. Therefore, the valence electron configuration of Silicon $\left(\text{Si}\right)$ is $3s^{2}3p^2$.

Explanation:

The number of valence electrons, the general valence electron configuration, a sample element and the specific valence electron configuration of the sample element for Group $5\text{A}$.

The Group $\text{5A}$ indicates that the outermost shell of all elements present in Group $\text{5A}$ have five electrons. Hence, the number of valence electrons present in Group $\text{5A}$ is five.

The valence electron in $\text{5A}$ is also present in $p$ orbital after filling the $s$ orbital as it accommodates maximum of two electrons. The general valence electron configuration of Group $\text{5A}$ is $n{s}^{2}n{p}^3$.

The sample element for this group is Antimony $\left(\text{Sb}\right)$ as it contains five electrons in its valence shell and therefore belongs to Group $\text{5A}$.

The atomic number of Antimony $\left(\text{Sb}\right)$ is $51$ and according to Hund’s rules the ground state electronic configuration of Antimony $\left(\text{Sb}\right)$ with preceding noble gas Krypton becomes $\left[\text{Kr}\right]5s^{2}4d^{10}5p^3$ with five valence electrons present in $5s\text{ and 5}p$ orbitals. Therefore, the valence electron configuration of Antimony $\left(\text{Sb}\right)$ is $5s^{2}5p^3$.

Explanation:

The number of valence electrons, the general valence electron configuration, a sample element and the specific valence electron configuration of the sample element for Group $\text{6A}$.

The Group $\text{6A}$ indicates that the outermost shell of all elements present in Group $\text{6A}$ have six electrons. Hence, the number of valence electrons present in Group $\text{6A}$ is six.

The valence electron in $\text{6A}$ is also present in $p$ orbital after filling the $s$ orbital as it accommodates maximum of two electrons. The general valence electron configuration of Group $\text{6A}$ is $n{s}^{2}n{p}^4$.

The sample element for this group is Polonium $\left(\text{Po}\right)$ as it contains six electrons in its valence shell and therefore belongs to Group $\text{6A}$.

The atomic number of Polonium $\left(\text{Po}\right)$ is $84$ and according to Hund’s rules the ground state electronic configuration of Polonium $\left(\text{Po}\right)$ with preceding noble gas Xenon becomes $\left[\text{Xe}\right]6s^{2}4f^{14}5d^{10}6p^4$ with six valence electrons present in $6s\text{ and 6}p$ orbitals. Therefore, the valence electron configuration of Polonium $\left(\text{Po}\right)$ is $6s^{2}6p^4$.

Explanation:

The number of valence electrons, the general valence electron configuration, a sample element and the specific valence electron configuration of the sample element for Group $7\text{A}$.

The Group $\text{7A}$ indicates that the outermost shell of all elements present in Group $\text{7A}$ have seven electrons. Hence, the number of valence electrons present in Group $\text{7A}$ is seven.

The valence electron in $\text{7A}$ is also present in $p$ orbital after filling the $s$ orbital as it accommodates maximum of two electrons. The general valence electron configuration of Group $\text{7A}$ is $n{s}^{2}n{p}^5$.

The sample element for this group is Chlorine $\left(\text{Cl}\right)$ as it contains seven electrons in its valence shell and therefore belongs to Group $\text{7A}$.

The atomic number of Chlorine $\left(\text{Cl}\right)$ is $17$ and according to Hund’s rules the ground state electronic configuration of Chlorine $\left(\text{Cl}\right)$ with preceding noble gas Neon becomes $\left[\text{Ne}\right]3s^{2}3p^5$ with seven valence electrons present in $3s\text{ and 3}p$ orbitals. Therefore, the valence electron configuration of Chlorine $\left(\text{Cl}\right)$ is $3s^{2}3p^5$.

Also, the sample element for this group is element ${117}^{\text{th}}$ as it contains seven electrons in its valence shell and therefore belongs to Group $\text{7A}$.

Hence, its atomic number is $117$ and according to Hund’s rules the ground state electronic configuration of element ${117}^{\text{th}}$ with preceding noble gas Radon becomes $\left[\text{Rn}\right]7s^{2}5f^{14}6d^{10}7p^5$ with seven valence electrons present in $7s\text{ and 7}p$ orbitals. Therefore, the valence electron configuration of element ${117}^{\text{th}}$ is $7s^{2}7p^5$.

Explanation:

The number of valence electrons, the general valence electron configuration, a sample element and the specific valence electron configuration of the sample element for Group $\text{8A}$.

The Group $\text{8A}$ indicates that the outermost shell of all elements present in Group $\text{8A}$ have eight electrons. Hence, the number of valence electrons present in Group $\text{8A}$ is eight.

The valence electron in $\text{8A}$ is also present in $p$ orbital after filling the $s$ orbital as it accommodates maximum of two electrons. The general valence electron configuration of Group $\text{8A}$ is $n{s}^{2}n{p}^6$.

The sample element for this group is Neon $\left(\text{Ne}\right)$ as it contains eight electrons in its valence shell and therefore belongs to Group $\text{8A}$.

The atomic number of Neon $\left(\text{Ne}\right)$ is $10$ and according to Hund’s rules the ground state electronic configuration of Neon $\left(\text{Ne}\right)$ is $\left[\text{Ne}\right]1s^{2}2s^{2}2p^6$ with eight valence electrons present in $2s\text{ and 2}p$ orbitals. Therefore, the valence electron configuration of Neon $\left(\text{Ne}\right)$ is $2s^{2}2p^6$.

Conclusion

• Group $\text{1A}$; the valence electron configuration of Lithium $\left(\text{Li}\right)$ is ${\text{2s}}^{\text{1}}$.
• Group $\text{2A}$; the valence electron configuration of Radium $\left(\text{Ra}\right)$ is $7s^2$.
• Group $\text{3A}$; the valence electron configuration of Gallium $\left(\text{Ga}\right)$ is $4s^{2}4p^1$.
• Group $\text{4A}$; the valence electron configuration of Silicon $\left(\text{Si}\right)$ is $3s^{2}3p^2$.
• Group $\text{5A}$; the valence electron configuration of Antimony $\left(\text{Sb}\right)$ is $5s^{2}5p^3$.
• Group $\text{6A}$; the valence electron configuration of Polonium $\left(\text{Po}\right)$ is $6s^{2}6p^4$.
• Group $\text{7A}$; the valence electron configuration of Chlorine $\left(\text{Cl}\right)$ is $3s^{2}3p^5$ and the valence electron configuration of element ${117}^{\text{th}}$ is $7s^{2}7p^5$.
• Group $\text{8A}$; the valence electron configuration of Neon $\left(\text{Ne}\right)$ is $2s^{2}2p^6$.