Chapter 12, Problem 88A

(a)

Interpretation Introduction

Interpretation: The number of electrons, protons, and neutrons in titanium-47 needs to be determined.

Concept Introduction: Isotopes are atoms of the same element with the same atomic number but different mass numbers. Thus, two isotopes have the same number of electrons and protons (equal to atomic number) but they have a different number of neutrons (the mass number is equal to the sum of the number of protons and neutrons).

Explanation of Solution

The given isotope is titanium-47. Thus, the mass number is 47. Now, the atomic number of titanium is 22; thus, the number of electrons and protons will be 22.

Now, the mass number is the sum of the number of protons and neutrons; thus, the number of neutrons in this isotope will be:

  $M=n_p+n_n$

Or,

  $n_n=M-n_p$

Substitute the values,

  $\begin{array}{c}{n}_n=47-22\\ =25\end{array}$

Thus, the number of electrons, protons, and neutrons in the given isotope are 22, 22, and, 25 respectively.

(b)

Interpretation Introduction

Interpretation: The number of electrons, protons, and neutrons in tin-120 needs to be determined.

Concept Introduction: Isotopes are atoms of the same element with the same atomic number but a different mass number. Thus, two isotopes have the same number of electrons and protons (equal to atomic number) but they have different numbers of neutrons (the mass number is equal to the sum of the number of protons and neutrons).

Explanation of Solution

The given isotope is tin-120. Thus, the mass number is 120. Now, the atomic number of tin is 50; thus, the number of electrons and protons will be 50.

Now, the mass number is the sum of the number of protons and neutrons; thus, the number of neutrons in this isotope will be:

  $M=n_p+n_n$

Or,

  $n_n=M-n_p$

Substitute the values,

  $\begin{array}{c}{n}_n=120-50\\ =70\end{array}$

Thus, the number of electrons, protons, and neutrons in the given isotope are 50, 50, and 70 respectively.

(c)

Interpretation Introduction

Interpretation: The number of electrons, protons, and neutrons in oxygen-18 needs to be determined.

Concept Introduction: Isotopes are atoms of the same element with the same atomic number but a different mass number. Thus, two isotopes have the same number of electrons and protons (equal to atomic number) but they have different numbers of neutrons (the mass number is equal to the sum of the number of protons and neutrons).

Explanation of Solution

The given isotope is oxygen-18. Thus, the mass number is 18. Now, the atomic number of oxygen is 8; thus, the number of electrons and protons will be 8.

Now, the mass number is the sum of the number of protons and neutrons; thus, the number of neutrons in this isotope will be:

  $M=n_p+n_n$

Or,

  $n_n=M-n_p$

Substitute the values,

  $\begin{array}{c}{n}_n=18-8\\ =10\end{array}$

Thus, the number of electrons, protons, and neutrons in the given isotope are 8, 8, and, 10 respectively.

(d)

Interpretation Introduction

Interpretation: The number of electrons, protons, and neutrons in magnesium-26 needs to be determined.

Concept Introduction: Isotopes are atoms of the same element with the same atomic number but a different mass number. Thus, two isotopes have the same number of electrons and protons (equal to atomic number) but they have different numbers of neutrons (the mass number is equal to the sum of the number of protons and neutrons).

Explanation of Solution

The given isotope is magnesium-26. Thus, the mass number is 26. Now, the atomic number of magnesium is 12; thus, the number of electrons and protons will be 12.

Now, the mass number is the sum of the number of protons and neutrons; thus, the number of neutrons in this isotope will be:

  $M=n_p+n_n$

Or,

  $n_n=M-n_p$

Substitute the values,

  $\begin{array}{c}{n}_n=26-12\\ =14\end{array}$

Thus, the number of electrons, protons, and neutrons in the given isotope are 12, 12, and, 14 respectively.