Chapter 2, Problem 2.13QP

Interpretation Introduction

Interpretation:

The number of protons, neutrons and electrons in given species has to be identified.

Concept Introduction:

Mass number(A): Mass number of an element is sum of protons and neutrons of the atom.

$\text{A= Number of protons}\left(\text{P}\right)\text{ + Number of neutrons}\left(\text{n}\right)$

Consider an element X with atomic number and mass number,

${}_Z^A\text{X}$

Where,

A is mass number and Z is atomic number ( number of proton or electron)

Answer to Problem 2.13QP

Number of proton, neutron and electrons for given species are given as follows.

Isotopes	${\text{He}}_{\text{2}}^3$	${\text{He}}_{\text{2}}^4$	${\text{Mg}}_{\text{12}}^{\text{24}}$	${\text{Mg}}_{\text{12}}^{\text{25}}$	${\text{Ti}}_{\text{22}}^{\text{48}}$	${\text{Br}}_{\text{35}}^{\text{79}}$	${\text{Pt}}_{\text{78}}^{\text{195}}$
No. of Protons	2	2	12	12	22	35	78
No. of Neutrons	1	2	12	13	26	44	117

Explanation of Solution

For ${\text{He}}_{\text{2}}^3$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X = }}_{\text{2}}^{\text{3}}\text{He}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 2}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 3 = 2 + n }\\ \text{n}\text{=1}\end{array}$

Thus, the number of neutrons, protons and electrons are found as $1$,$2$ and $2$ respectively.

For ${\text{He}}_{\text{2}}^4$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X = }}_{\text{2}}^4\text{He}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 2}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 4 = 2 + n }\\ \text{n}\text{=2}\end{array}$

Thus, the number of neutrons, protons and electrons are found as $2$,$2$ and $2$ respectively.

For ${\text{Mg}}_{\text{12}}^{\text{24}}$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X = Mg}}_{\text{12}}^{\text{24}}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 12}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 24 = 12 + n }\\ \text{n}\text{=12}\end{array}$

Thus, the number of neutrons, protons and electrons are found as $12$,$12$ and $12$ respectively.

For ${\text{Mg}}_{\text{12}}^{\text{25}}$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X = Mg}}_{\text{12}}^{\text{25}}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 12}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 25 = 12 + n }\\ \text{n}\text{=13}\end{array}$

Thus, the number of neutrons, protons and electrons are found as $13$,$12$ and $12$ respectively.

For ${\text{Ti}}_{\text{22}}^{\text{48}}$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X =Ti}}_{\text{22}}^{\text{48}}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 22}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 48 = 22 + n }\\ \text{n}\text{=26}\end{array}$

Thus, the number of neutrons, protons and electrons are found as $26$,$22$ and $22$ respectively.

For ${\text{Br}}_{35}^{79}$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X =Br}}_{35}^{79}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 35}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 79 = 35 + n }\\ \text{n}\text{= 44}\end{array}$

Thus, the number of neutrons, protons and electrons are found as $44$,$35$ and $35$ respectively.

For ${\text{Pt}}_{\text{78}}^{\text{195}}$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X = Pt}}_{\text{78}}^{\text{195}}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 78}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 195 = 78 + n }\\ \text{n}\text{= 117}\end{array}$

Thus, the number of neutrons, protons and electrons are found as $117$,$78$ and $78$ respectively.

Conclusion

The number of protons, neutrons and electrons in given species were identified.