Chapter 2.2, Problem 2.13P

(a)

Interpretation Introduction

Interpretation:

The mass number of an atom that contains $42$ protons and electrons and $53$ neutrons has to be given.

Concept Introduction:

Mass number (A):

Mass number of an element is defined as the total number of protons and neutrons in an atom.

  $\text{A=Number}\text{of}\text{protons}\text{+}\text{Number}\text{of}\text{neutrons}$

(b)

Interpretation Introduction

Interpretation:

The mass number of an atom that contains $24$ protons and electrons and $28$ neutrons has to be given.

Concept Introduction:

Refer to part (a).