Chapter 2, Problem 41E

(a)

Interpretation Introduction

Interpretation: The numbers of protons, neutrons and electrons present in ${}_{\text{92}}^{\text{235}}\text{U}$ are to be stated.

Concept introduction: In a neutral atom, the number of electrons present are equal to protons. These two are also equivalent to the atomic number in case of neutral atoms. The number of neutrons is calculated by taking the difference in mass number and atomic number. This is because mass number is calculated by taking sum of number of protons and number of neutrons.

Answer to Problem 41E

The numbers of protons, neutrons and electrons present in ${}_{\text{92}}^{\text{235}}\text{U}$ are $92,143$ and $92$ respectively.

Explanation of Solution

The element given is ${}_{\text{92}}^{\text{235}}\text{U}$ .

In this notation of elements, the subscript represents the atomic number and superscript represents the mass number.

So, the atomic number of ${}_{\text{92}}^{\text{235}}\text{U}$ is $92$ and mass number is equal to $235$ . Atomic number is equivalent to number of protons, thus, number of proton is $92$ .

Since it is a neutral species, therefore, number of electron is also equal to $92$ .

The formula used for the calculation of number of neutrons is shown below.

  $\text{Number}\text{of}\text{neutrons}=\text{Mass}\text{number}-\text{Atomic}\text{number}$

Substitute the value of mass number and atomic number of ${}_{\text{92}}^{\text{235}}\text{U}$ in the above formula.

  $\begin{array}{c}\text{Number}\text{of}\text{neutrons}=\text{Mass}\text{number}-\text{Atomic}\text{number}\\ =\text{235}-\text{92}\\ =\text{143}\end{array}$

Therefore, the number of neutrons in ${}_{\text{92}}^{\text{235}}\text{U}$ is $143$ .

(b)

Interpretation Introduction

Interpretation: The numbers of protons, neutrons and electrons present in ${}_{13}^{\text{27}}\text{Al}$ are to be stated.

Concept introduction: In a neutral atom, the number of electrons present are equal to protons. These two are also equivalent to the atomic number in case of neutral atoms. The number of neutrons is calculated by taking the difference in mass number and atomic number. This is because mass number is calculated by taking sum of number of protons and number of neutrons.

Answer to Problem 41E

The numbers of protons, neutrons and electrons present in ${}_{13}^{\text{27}}\text{Al}$ are $13,14$ and $13$ respectively.

Explanation of Solution

The element given is ${}_{13}^{\text{27}}\text{Al}$ .

In this notation of elements, the subscript represents the atomic number and superscript represents the mass number.

So, the atomic number of ${}_{13}^{\text{27}}\text{Al}$ is $13$ and mass number is equal to $27$ . Atomic number is equivalent to number of protons, thus, number of proton is $13$ .

Since it is a neutral species, therefore, number of electron is also equal to $13$ .

The formula used for the calculation of number of neutrons is shown below.

  $\text{Number}\text{of}\text{neutrons}=\text{Mass}\text{number}-\text{Atomic}\text{number}$

Substitute the value of mass number and atomic number of ${}_{13}^{\text{27}}\text{Al}$ in the above formula.

  $\begin{array}{c}\text{Number}\text{of}\text{neutrons}=\text{Mass}\text{number}-\text{Atomic}\text{number}\\ =\text{27}-13\\ =\text{14}\end{array}$

Therefore, the number of neutrons in ${}_{13}^{\text{27}}\text{Al}$ is $14$ .

(c)

Interpretation Introduction

Interpretation: The numbers of protons, neutrons and electrons present in ${}_{26}^{\text{57}}\text{Fe}$ are to be stated.

Concept introduction: In a neutral atom, the number of electrons present are equal to protons. These two are also equivalent to the atomic number in case of neutral atoms. The number of neutrons is calculated by taking the difference in mass number and atomic number. This is because mass number is calculated by taking sum of number of protons and number of neutrons.

Answer to Problem 41E

The numbers of protons, neutrons and electrons present in ${}_{26}^{\text{57}}\text{Fe}$ are $26,31$ and $26$ respectively.

Explanation of Solution

The element given is ${}_{26}^{\text{57}}\text{Fe}$ .

In this notation of elements, the subscript represents the atomic number and superscript represents the mass number.

So, the atomic number of ${}_{26}^{\text{57}}\text{Fe}$ is $26$ and mass number is equal to $57$ . Atomic number is equivalent to number of protons, thus, number of proton is $26$ .

Since it is a neutral species, therefore, number of electron is also equal to $26$ .

The formula used for the calculation of number of neutrons is shown below.

  $\text{Number}\text{of}\text{neutrons}=\text{Mass}\text{number}-\text{Atomic}\text{number}$

Substitute the value of mass number and atomic number of ${}_{26}^{\text{57}}\text{Fe}$ in the above formula.

  $\begin{array}{c}\text{Number}\text{of}\text{neutrons}=\text{Mass}\text{number}-\text{Atomic}\text{number}\\ =5\text{7}-26\\ =\text{31}\end{array}$

Therefore, the number of neutrons in ${}_{26}^{\text{57}}\text{Fe}$ is $31$ .

(d)

Interpretation Introduction

Interpretation: The numbers of protons, neutrons and electrons present in ${}_{82}^{208}\text{Pb}$ are to be stated.

Concept introduction: In a neutral atom, the number of electrons present are equal to protons. These two are also equivalent to the atomic number in case of neutral atoms. The number of neutrons is calculated by taking the difference in mass number and atomic number. This is because mass number is calculated by taking sum of number of protons and number of neutrons.

Answer to Problem 41E

The numbers of protons, neutrons and electrons present in ${}_{82}^{208}\text{Pb}$ are $82,126$ and $82$ respectively.

Explanation of Solution

The element given is ${}_{82}^{208}\text{Pb}$ .

In this notation of elements, the subscript represents the atomic number and superscript represents the mass number.

So, the atomic number of ${}_{82}^{208}\text{Pb}$ is $82$ and mass number is equal to $208$ . Atomic number is equivalent to number of protons, thus, number of proton is $82$ .

Since it is a neutral species, therefore, number of electron is also equal to $82$ .

The formula used for the calculation of number of neutrons is shown below.

  $\text{Number}\text{of}\text{neutrons}=\text{Mass}\text{number}-\text{Atomic}\text{number}$

Substitute the value of mass number and atomic number of ${}_{82}^{208}\text{Pb}$ in the above formula.

  $\begin{array}{c}\text{Number}\text{of}\text{neutrons}=\text{Mass}\text{number}-\text{Atomic}\text{number}\\ =208-82\\ =126\end{array}$

Therefore, the number of neutrons in ${}_{82}^{208}\text{Pb}$ is $126$ .

(e)

Interpretation Introduction

Interpretation: The numbers of protons, neutrons and electrons present in ${}_{37}^{86}\text{Rb}$ are to be stated.

Concept introduction: In a neutral atom, the number of electrons present are equal to protons. These two are also equivalent to the atomic number in case of neutral atoms. The number of neutrons is calculated by taking the difference in mass number and atomic number. This is because mass number is calculated by taking sum of number of protons and number of neutrons.

Answer to Problem 41E

The numbers of protons, neutrons and electrons present in ${}_{37}^{86}\text{Rb}$ are $37,49$ and $37$ respectively.

Explanation of Solution

The element given is ${}_{37}^{86}\text{Rb}$ .

In this notation of elements, the subscript represents the atomic number and superscript represents the mass number.

So, the atomic number of ${}_{37}^{86}\text{Rb}$ is $37$ and mass number is equal to $86$ . Atomic number is equivalent to number of protons, thus, number of proton is $37$ .

Since it is a neutral species, therefore, number of electron is also equal to $37$ .

The formula used for the calculation of number of neutrons is shown below.

  $\text{Number}\text{of}\text{neutrons}=\text{Mass}\text{number}-\text{Atomic}\text{number}$

Substitute the value of mass number and atomic number of ${}_{37}^{86}\text{Rb}$ in the above formula.

  $\begin{array}{c}\text{Number}\text{of}\text{neutrons}=\text{Mass}\text{number}-\text{Atomic}\text{number}\\ =86-37\\ =49\end{array}$

Therefore, the number of neutrons in ${}_{37}^{86}\text{Rb}$ is $49$ .

(f)

Interpretation Introduction

Interpretation: The numbers of protons, neutrons and electrons present in ${}_{20}^{41}\text{Ca}$ are to be stated.

Concept introduction: In a neutral atom, the number of electrons present are equal to protons. These two are also equivalent to the atomic number in case of neutral atoms. The number of neutrons is calculated by taking the difference in mass number and atomic number. This is because mass number is calculated by taking sum of number of protons and number of neutrons.

Answer to Problem 41E

The numbers of protons, neutrons and electrons present in ${}_{20}^{41}\text{Ca}$ are $20,21$ and $20$ respectively.

Explanation of Solution

The element given is ${}_{20}^{41}\text{Ca}$ .

In this notation of elements, the subscript represents the atomic number and superscript represents the mass number.

So, the atomic number of ${}_{20}^{41}\text{Ca}$ is $20$ and mass number is equal to $41$ . Atomic number is equivalent to number of protons, thus, number of proton is $20$ .

Since it is a neutral species, therefore, number of electron is also equal to $20$ .

The formula used for the calculation of number of neutrons is shown below.

  $\text{Number}\text{of}\text{neutrons}=\text{Mass}\text{number}-\text{Atomic}\text{number}$

Substitute the value of mass number and atomic number of ${}_{20}^{41}\text{Ca}$ in the above formula.

  $\begin{array}{c}\text{Number}\text{of}\text{neutrons}=\text{Mass}\text{number}-\text{Atomic}\text{number}\\ =41-20\\ =21\end{array}$

Therefore, the number of neutrons in ${}_{20}^{41}\text{Ca}$ is $21$ .