Chapter 4.3, Problem 34LC

(a)

Interpretation Introduction

Interpretation : The number of protons, neutrons,and electrons present in each pair of isotopes is to be calculated.

Concept Introduction : Isotopes are the elements having same atomic number but different mass numbers. An element can have two or more isotopes.

Answer to Problem 34LC

In ${}_3^6\text{Li}$ , there are $3$ protons, $3$ electrons, and $3$ neutrons.

In ${}_3^7\text{Li}$ , there are $3$ protons, $3$ electrons, and $4$ neutrons.

Explanation of Solution

The count of protons present in the nucleus of the atom gives the atomic number.

The count of protons and neutrons present in the nucleus of the atom gives the mass number.

The general representation symbol of an element is given as ${}_{\text{Z}}^{\text{A}}\text{X}$ .

Where, $X$ is the element, $Z$ is the atomic number, and $A$ is the atomic number.

The number of protons, number of electrons, and atomic number are always equal for a given element of the isotope.

So, for the given isotopes of Lithium, there are $3$ protons and $3$ electrons.

The formula to calculate the number of neutrons is given as:

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

In the given isotope ${}_3^6\text{Li}$ , the mass number is $6$ and the number of protons is $3$ .

Substitute the values in the above formula to calculate the number of neutrons.

  $\begin{array}{c}\text{Number of neutrons}\text{=}\text{Mass number}-\text{Number of protons}\\ \text{=}6-3\\ =3\end{array}$

Similarly, calculate the number of neutrons in the given isotope ${}_3^7\text{Li}$ .

In ${}_3^7\text{Li}$ , the mass number is $7$ and the number of protons is $3$ .

Substitute the values in the above formula to calculate the number of neutrons.

  $\begin{array}{c}\text{Number of neutrons}\text{=}\text{Mass number}-\text{Number of protons}\\ \text{=}7-3\\ =4\end{array}$

The number of neutrons in ${}_3^6\text{Li}$ and ${}_3^7\text{Li}$ are $3$ and $4$ respectively.

(b)

Interpretation Introduction

Interpretation : The number of protons, neutrons,and electrons present in each pair of isotopes is to be calculated.

Concept Introduction : Isotopes are the elements having same atomic number but different mass numbers. An element can have two or more isotopes.

Answer to Problem 34LC

In ${}_{20}^{42}\text{Ca}$ , there are $20$ protons, $20$ electrons, and $22$ neutrons.

In ${}_{20}^{44}\text{Ca}$ , there are $20$ protons, $20$ electrons, and $24$ neutrons.

Explanation of Solution

The count of protons present in the nucleus of the atom gives the atomic number.

The count of protons and neutrons present in the nucleus of the atom gives the mass number.

The general representation symbol of an element is given as ${}_{\text{Z}}^{\text{A}}\text{X}$ .

Where, $X$ is the element, $Z$ is the atomic number, and $A$ is the atomic number.

The number of protons, number of electrons, and atomic number are always equal for a given element of the isotope.

So, for the given isotopes of Calcium, there are $20$ protons and $20$ electrons.

The number of neutrons in an element is the difference between the mass number and the number of protons in an element.

The formula to calculate the number of neutrons is given as:

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

In the given isotope ${}_{20}^{42}\text{Ca}$ , the mass number is $42$ and the number of protons is $20$ .

Substitute the values in the above formula to calculate the number of neutrons.

  $\begin{array}{c}\text{Number of neutrons}\text{=}\text{Mass number}-\text{Number of protons}\\ \text{=}42-20\\ =22\end{array}$

Similarly, calculate the number of neutrons in the given isotope ${}_{20}^{44}\text{Ca}$ .

In ${}_{20}^{44}\text{Ca}$ , the mass number is $44$ and the number of protons is $20$ .

Substitute the values in the above formula to calculate the number of neutrons.

  $\begin{array}{c}\text{Number of neutrons}\text{=}\text{Mass number}-\text{Number of protons}\\ \text{= 44}-20\\ =24\end{array}$

The number of neutrons in ${}_{20}^{42}\text{Ca}$ and ${}_{20}^{44}\text{Ca}$ are $22$ and $24$ respectively.

(c)

Interpretation Introduction

Interpretation : The number of protons, neutrons,and electrons present in each pair of isotopes is to be calculated.

Concept Introduction : Isotopes are the elements having same atomic number but different mass numbers. An element can have two or more isotopes.

Answer to Problem 34LC

In ${}_{34}^{78}\text{Se}$ , there are $34$ protons, $34$ electrons, and $44$ neutrons.

In ${}_{34}^{80}\text{Se}$ , there are $34$ protons, $34$ electrons, and $46$ neutrons.

Explanation of Solution

The count of protons present in the nucleus of the atom gives the atomic number.

The count of protons and neutrons present in the nucleus of the atom gives the mass number.

The general representation symbol of an element is given as ${}_{\text{Z}}^{\text{A}}\text{X}$ .

Where, $X$ is the element, $Z$ is the atomic number, and $A$ is the atomic number.

The number of protons, number of electrons, and atomic number are always equal for a given element of the isotope.

So, for the given isotopes of Selenium, there are $34$ protons and $34$ electrons.

The number of neutrons in an element is the difference between the mass number and the number of protons in an element.

The formula to calculate the number of neutrons is given as:

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

In the given isotope ${}_{34}^{78}\text{Se}$ , the mass number is $78$ and the number of protons is $34$ .

Substitute the values in the above formula to calculate the number of neutrons.

  $\begin{array}{c}\text{Number of neutrons}\text{=}\text{Mass number}-\text{Number of protons}\\ \text{=}78-34\\ =44\end{array}$

Similarly, calculate the number of neutrons in the given isotope ${}_{34}^{80}\text{Se}$ .

In ${}_{34}^{80}\text{Se}$ , the mass number is $80$ and the number of protons is $34$ .

Substitute the values in the above formula to calculate the number of neutrons.

  $\begin{array}{c}\text{Number of neutrons}\text{=}\text{Mass number}-\text{Number of protons}\\ \text{=}80-34\\ =46\end{array}$

The number of neutrons in ${}_{34}^{78}\text{Se}$ and ${}_{34}^{80}\text{Se}$ are $44$ and $46$ respectively.