Chapter 2, Problem 2.14QP

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 2.14QP

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

Isotopes	${\text{N}}_{\text{7}}^{\text{15}}$	${\text{S}}_{\text{16}}^{\text{33}}$	${\text{Cu}}_{\text{29}}^{\text{63}}$	${\text{Sr}}_{\text{38}}^{\text{84}}$	${\text{Ba}}_{\text{56}}^{\text{130}}$	${\text{W}}_{\text{74}}^{\text{186}}$	${\text{Hg}}_{\text{80}}^{\text{202}}$
No. of Protons	7	16	29	38	56	74	80
No. of Neutrons	8	17	34	46	74	112	122
No. of Electrons	7	16	29	38	56	74	80

Explanation of Solution

For ${\text{N}}_{\text{7}}^{\text{15}}$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X =N}}_{\text{7}}^{\text{15}}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 7}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 15 = 7 + n }\\ \text{n}\text{=8}\end{array}$

For ${\text{S}}_{\text{16}}^{\text{33}}$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X =S}}_{\text{16}}^{\text{33}}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 16}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 33 = 16 + n }\\ \text{n}\text{=17}\end{array}$

For ${\text{Cu}}_{\text{29}}^{\text{63}}$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X = Cu}}_{\text{29}}^{\text{63}}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 29}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 63 = 29 + n }\\ \text{n}\text{=34}\end{array}$

For ${\text{Sr}}_{\text{38}}^{\text{84}}$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X = Sr}}_{\text{38}}^{\text{84}}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 38}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 84 = 38 + n }\\ \text{n}\text{= 46}\end{array}$

For ${\text{Ba}}_{\text{56}}^{\text{130}}$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X =Ba}}_{\text{56}}^{\text{130}}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 56}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 130 = 56 + n }\\ \text{n}\text{=74}\end{array}$

For ${\text{W}}_{\text{74}}^{\text{186}}$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X =W}}_{\text{74}}^{\text{186}}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 74}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 186 = 74 + n }\\ \text{n}\text{= 112}\end{array}$

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

For ${\text{Hg}}_{\text{80}}^{\text{202}}$, the number of protons, neutrons, and electrons is calculated as follows,

$\begin{array}{l}{}_{\text{Z}}^{\text{A}}{\text{X = Hg}}_{\text{80}}^{\text{202}}\\ \text{Z (atomic number) = Number of protons (number of protons are equalent to number of electrons)}\\ \text{= 80}\\ \text{A (mass number) = Number of protons (P) + Number of neutrons (N)}\\ \text{ 202 = 80 + n }\\ \text{n}\text{= 122}\end{array}$

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.