Chapter 4, Problem 72A

Interpretation Introduction

Interpretation:

The table of properties of chlorine and zirconium is to be completed.

Concept introduction:

Isotopes of an element have same Atomic Number and different Mass number. The atomic symbol of an atom is represented as follows:

$\text{X}$

Where, $\text{A = Mass number}$

$\text{Z = Atomic number}$

Answer to Problem 72A

Element	Cl	Cl	Zr	Zr
Atomic number	17	17	40	40
Mass number	35	37	90	92
Protons	17	17	40	40
Neutrons	18	20	50	52
Electrons	17	17	40	40

Explanation of Solution

In the given table, isotopes of Chlorine and Zirconium Elements are given.

Thus, Atomic number will be same and Mass number will be different for isotopes of same element.

$\text{Atomic number = Number of protons}$

$\text{Number of protons = Number of electrons}$

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

Chlorine atom with Mass number 35

$\begin{array}{l}\text{Number of protons = Atomic number }\left(\text{Given}\right)\hfill \\ \text{ = 17}\hfill \end{array}$

$\begin{array}{l}\text{Number of electrons = Number of protons}\hfill \\ \text{ = 17}\hfill \end{array}$

$\begin{array}{l}\text{Number of neutrons = Mass number – Atomic number}\hfill \\ \text{ = 35 – 17}\hfill \\ \text{ = 18}\hfill \end{array}$

Chlorine atom with Mass number 37

$\begin{array}{l}\text{Number of protons = Atomic number = Number of electrons }\left(\text{Given}\right)\\ \text{ =17}\end{array}$

$\begin{array}{l}\text{Number of neutrons = Mass number – Atomic number}\hfill \\ \text{ = 37 – 17}\hfill \\ \text{ = 20}\hfill \end{array}$

Zirconium atom with 50 neutrons

$\begin{array}{l}\text{Number of protons = Atomic number }\left(\text{Given}\right)\hfill \\ \text{ = 40}\hfill \end{array}$

$\begin{array}{l}\text{Number of electrons = Number of protons}\hfill \\ \text{ = 40}\hfill \end{array}$

$\begin{array}{l}\text{Mass number = Number of neutrons + Atomic number}\hfill \\ \text{ = 50 + 40}\hfill \\ \text{ = 90}\hfill \end{array}$

Zirconium atom with mass number 92

$\begin{array}{l}\text{Atomic number = number electrons = number of protons }\left(\text{Given}\right)\\ \text{ = 40}\end{array}$

Number of neutrons = Mass number − Atomic number

= 92 − 40

= 52

Thus,

Element	Cl	Cl	Zr	Zr
Atomic number	17	17	40	40
Mass number	35	37	90	92
Protons	17	17	40	40
Neutrons	18	20	50	52
Electrons	17	17	40	40

Conclusion

Isotopes of an element have same number of protons and electrons but different number of neutrons.

$\text{C}\text{l}$ And $\text{C}\text{l}$ are isotopes of Chlorine Element

$\text{Z}\text{r}$ And $\text{Z}\text{r}$ are isotopes of Zirconium Element