Chapter 16.2, Problem 6R

To determine

The mass number and the atomic number of a chlorine atom.

Explanation of Solution

Introduction:

The atomic number differentiates one element from another. 

Explanation: 

From the periodic table, the chlorine atom has 17 protons and 18 neutrons. The atomic number is based on the number of protons in the element. So, the atomic number of chlorine is 17 because the number of protons of chlorine is 17.

The mass number is defined as the sum of neutrons and protons. Therefore, the mass number of Chlorine is 35 $\left(18+17=35\right)$ .

Conclusion: 

From the periodic table, the atomic number and atomic mass can be determined directly. The sum of neutrons and protons results is the atomic mass.