Chapter 14, Problem 108A

Interpretation Introduction

Interpretation: The number of electrons, protons, and neutrons needs to be determined in an atom of lead. The molar mass of lead is given 206.

Concept Introduction: In an atom, the number of protons is equal to the number of electrons. This is the atomic number of the atom of an element in the periodic table. The atomic mass of an atom is equal to the sum of the number of protons and neutrons.

Explanation of Solution

The given element is lead-206. This is the atomic mass of the lead. Now, atomic mass is related to the number of protons and neutrons as follows:

  $\text{Atomic mass}={\text{n}}_p+n_n$

Also, the atomic number is equal to the number of protons and the number of electrons. Here, the atomic number of lead is 82; thus, the number of protons and the number of electrons in lead is equal to 82.

Use the number of protons and atomic mass to calculate the number of neutrons as follows:

  $n_n=\text{Atomic mass}-{\text{n}}_p$

Substitute the values,

  $\begin{array}{c}{n}_n=\text{206}-82\\ =124\end{array}$

Thus, the number of neutrons in lead is 124.

Therefore, in lead-206, the number of protons, electrons, and neutrons is 82, 82, and 124 respectively.