Chapter U1.12, Problem 2E

Interpretation Introduction

Interpretation:

The significance of atomic mass should be stated.

Concept introduction:

Atoms are the tiny particles that are made of sub particles; electrons, protons and neutrons. They cannot be seen with naked eyes.

Answer to Problem 2E

The mass number is calculated by taking the sum of the number of neutrons and number of protons in a nucleus of an atom.

Explanation of Solution

The mass number is equal to the sum of the number of protons and neutrons of an atom. There are different elements with same mass number are known as isobars.

For example, the atomic number of carbon is 6. The number of protons in C is 6 and there are 6 neutrons in C.

The atomic mass of the carbon is calculated as follows:

$\begin{array}{c}\text{atomic}\text{mass}=\text{number}\text{of}\text{protons}+\text{number}\text{of}\text{neutrons}\\ =6+6\\ =12\end{array}$

Therefore, the atomic mass of the carbon is 12.

Conclusion

The mass number represents the sum of the number of neutrons and number of protons in a nucleus.