Chapter 2, Problem 2.90QP

(a)

Interpretation Introduction

Interpretation:

The given electron configuration $1s^{2}1p^2$ is possible or not possible, identify the correct element and its correct electron configuration have to be mentioned.

Concept Introduction:

Aufbau principle says that electron fills the lowest energy level before filling the higher ones.

Figure 1

Explanation of Solution

Given electron configuration is $1s^{2}1p^2.$

The above electron configuration is wrong because the $1p$ orbital doesn’t exist and also electrons are filled based on Aufbau principle so, the configuration should be ${\text{1s}}^{\text{2}}{\text{2s}}^{\text{2}}$ not $1s^{2}1p^2.$  Hence, the electron configuration is $1s^{2}1p^2$ not possible.

The correct element and it electron configuration is $[Be]:1s^{2}2s^2.$

(b)

Interpretation Introduction

Interpretation:

The given electron configuration $1s^{2}2s^{2}2p^2$ is possible or not possible, identify the correct element and its correct electron configuration have to be mentioned.

Concept Introduction:

Refer to part (a).

Explanation of Solution

Given electron configuration is $1s^{2}2s^{2}2p^2$

The above electron configuration is right because the $1s^{2}2s^{2}2p^2$ orbital does exist and also electrons are filled based on Aufbau principle so, the configuration should be $1s^{2}2s^{2}2p^2.$

The electron configuration is $1s^{2}2s^{2}2p^2$ possible.

The correct element and it electron configuration is $[C]:1s^{2}2s^{2}2p^2.$

(c)

Interpretation Introduction

Interpretation:

The given electron configuration $2s^{2}2s^{2}2p^{6}2d^1$ is possible or not possible, identify the correct element and its correct electron configuration have to be mentioned.

Concept Introduction:

Refer to part (a).

Explanation of Solution

Given electron configuration is $2s^{2}2s^{2}2p^{6}2d^1$

The above electron configuration is wrong because two times $2s^{2}2s^{2}2p^{6}2d^1$ orbital doesn’t exist and also electrons are filled based on Aufbau principle so, the configuration should be $1s^{2}2s^{2}2p^{6}3d^1$ not $2s^{2}2s^{2}2p^{6}2d^1.$  Hence, the electron configuration is $2s^{2}2s^{2}2p^{6}2d^1$ not possible.

Hence, the correct element and it electron configuration is $[Na]:1s^{2}2s^{2}2p^{6}3s^1.$

(d)

Interpretation Introduction

Interpretation:

The given electron configuration $1s^{2}2s^3$ is possible or not possible, identify the correct element and its correct electron configuration have to be mentioned.

Concept Introduction:

Refer to part (a).

Explanation of Solution

Given electron configuration is $1s^{2}2s^3.$

The above electron configuration is wrong as the $2s^3$ orbital doesn’t exist because, the maximum number of electrons that can be accommodate in the s-orbital is two and also electrons are filled based on Aufbau principle so, the electron configuration should be ${\text{1s}}^{\text{2}}{\text{2s}}^{\text{2}}{\text{2p}}^{\text{1}}$ not $1s^{2}2s^3.$  The electron configuration is $1s^{2}2s^3$ not possible.

Hence, the correct element and it electron configuration is $[B]:1s^{2}2s^{2}2p^1.$