Question

The element lead (pb) consists of four naturally occurring isotopes with atomic masses 203.97302,205.97444,206.97587, n 207.97663 amu. the relative abundances of these four isotopes are 1.4,24.1,22.1, and 52.4 %, respectively. write the most common isotope of lead in two ways

Answer 1

The method of determining the most common isotope of lead is by determining the average atomic mass. The formula for determining the average atomic mass is:

$average atomic mass = \Sigma {percent abundance}\times {atomic mass}$

Substituting the values in the formula:

$average atomic mass = \frac{{203.97302}\times {1.4}+{205.9744}\times {24.1}+{206.97587}\times {22.1}+{207.97663}\times {52.4}}{100}$

$average atomic mass = \frac{285.562228+4963.984004+4574.166727+10897.975412}{100}$

$average atomic mass = \frac{20721.688371}{100} = 207.22 amu$

The most common isotope of lead is:

Lead - 207.22 amu

The atomic symbol of lead is $Pb$. The atomic number of $Pb$ is 82.

So, the the most common isotope of lead can be written as:

$_{207.22}^{82}Pb$ and Lead - 207.22 amu.