Chapter 4, Problem 69A

Xenon An isotope of xenon has an atomic number of 54 and contains 77 neutrons. What is the xenon isotope’s mass number?

Interpretation Introduction

Interpretation:

Mass number of xenon isotope needs to be calculated, if atomic number is 54 and there are 77 neutrons present in an atom.

Concept introduction:

Mass number is the sum of number of protons and neutrons present in the nucleus of an atom.

Answer to Problem 69A

$\text{Mass number = 131}$

Explanation of Solution

Atomic number of an atom is also referred as number of protons in an atom.

Atomic number = Number of protons

Number of protons = 54

Mass number is the total number of protons and neutrons present in the nucleus of an atom.

$\begin{array}{l}\text{Mass Number = Number of protons + Number of neutrons}\hfill \\ \text{ = 54 + 77}\hfill \\ \text{ = 131}\hfill \end{array}$

Mass number of xenon isotope is 131.

Conclusion

Xenon isotope with Atomic number 54 and 77 neutrons have mass number of 131.