Chapter 11, Problem 45E

Interpretation Introduction

(a)

Interpretation:

The element having the electron configuration $\left[\text{He}\right]2s^{2}2p^3$ is to be identified.

Concept introduction:

Electronic configuration represents the arrangement of electrons in an atom. The sublevels are filled according to their increasing energy. The electrons are firstly filled into the sublevel having the lowest energy. The sublevel closest to the nucleus has the lowest energy. The trend of filling of electrons according to the energy of sublevels is given below.

$1s<2s<2p<3s<3p<4s<3d<4p<5s<4d<5p<6s$

The electronic configuration up to the electronic configuration of the last noble gas is represented with the symbol of noble gas in square brackets. This notation is known as core notation.

Answer to Problem 45E

The element having the electron configuration $\left[\text{He}\right]2s^{2}2p^3$ is nitrogen.

Explanation of Solution

The given electron configuration is $\left[\text{He}\right]2s^{2}2p^3$. This gives total number of electrons as the sum of electrons in helium $\left(2\right)$, $2$ electrons in sublevel $2s$ and $3$ electrons in shell $2p$ which is equivalent to $7$. The atomic number of an element is equivalent to the number of electrons or protons. Therefore, the atomic number of element having configuration $\left[\text{He}\right]2s^{2}2p^3$ is $7$.

The element having atomic number $7$ is nitrogen.

Therefore, the element having the electron configuration $\left[\text{He}\right]2s^{2}2p^3$ is nitrogen.

Conclusion

The element having the electron configuration $\left[\text{He}\right]2s^{2}2p^3$ is nitrogen.

Interpretation Introduction

(b)

Interpretation:

The element having the electron configuration $\left[\text{Ne}\right]3s^{2}3p^1$ is to be identified.

Concept introduction:

Electronic configuration represents the arrangement of electrons in an atom. The sublevels are filled according to their increasing energy. The electrons are firstly filled into the sublevel having the lowest energy. The sublevel closest to the nucleus has the lowest energy. The trend of filling of electrons according to the energy of sublevels is given below.

$1s<2s<2p<3s<3p<4s<3d<4p<5s<4d<5p<6s$

The electronic configuration up to the electronic configuration of the last noble gas is represented with the symbol of noble gas in square brackets. This notation is known as core notation.

Answer to Problem 45E

The element having the electron configuration $\left[\text{Ne}\right]3s^{2}3p^1$ is aluminum.

Explanation of Solution

The given electron configuration is $\left[\text{Ne}\right]3s^{2}3p^1$. This gives total number of electrons as the sum of electrons in neon $\left(10\right)$, $1$ electron in sublevel $3p$ and $2$ electrons in sublevel $3s$ which is equivalent to $13$. The atomic number of an element is equivalent to the number of electrons or protons. Therefore, the atomic number of element having configuration $\left[\text{Ne}\right]3s^{2}3p^1$ is $13$.

The element having atomic number $13$ is aluminum.

Therefore, the element having the electron configuration $\left[\text{Ne}\right]3s^{2}3p^1$ is aluminum.

Conclusion

The element having the electron configuration $\left[\text{Ne}\right]3s^{2}3p^1$ is aluminum.

Interpretation Introduction

(c)

Interpretation:

The element having the electron configuration $\left[\text{Ar}\right]4s^{2}3d^7$ is to be identified.

Concept introduction:

Electronic configuration represents the arrangement of electrons in an atom. The sublevels are filled according to their increasing energy. The electrons are firstly filled into the sublevel having the lowest energy. The sublevel closest to the nucleus has the lowest energy. The trend of filling of electrons according to the energy of sublevels is given below.

$1s<2s<2p<3s<3p<4s<3d<4p<5s<4d<5p<6s$

The electronic configuration up to the electronic configuration of the last noble gas is represented with the symbol of noble gas in square brackets. This notation is known as core notation.

Answer to Problem 45E

The element having the electron configuration $\left[\text{Ar}\right]4s^{2}3d^7$ is cobalt.

Explanation of Solution

The given electron configuration is $\left[\text{Ar}\right]4s^{2}3d^7$. This gives total number of electrons as the sum of electrons in argon $\left(18\right)$, $7$ electrons in sublevel $3d$ and $2$ electrons in sublevel $4s$ which is equivalent to $27$. The atomic number of an element is equivalent to the number of electrons or protons. Therefore, the atomic number of element having configuration $\left[\text{Ar}\right]4s^{2}3d^7$ is $27$.

The element having atomic number $27$ is cobalt.

Therefore, the element having the electron configuration $\left[\text{Ar}\right]4s^{2}3d^7$ is cobalt.

Conclusion

The element having the electron configuration $\left[\text{Ar}\right]4s^{2}3d^7$ is cobalt.