Question

An element has four naturally occurring isotopes with the masses and natural abundances given in the table below. Find the atomic mass of the element (express your answer to four significant figures and include the appropriate units).

Isotope Mass (amu) Abundance (%)
1 203.97304 1.390
2 205.97447 24.11
3 206.97590 22.09
4 207.97665 52.41
Identify the element, by spelling out its full name.

Answer 1

Lead (Pb)

Step-by-step explanation:

To find the atomic mass of the element, we need to take into consideration all the naturally occurring isotopes. We then find the atomic mass by multiplying the natural abundance of the isotopes by their mass for all of the isotopes and summing them together.

1. 1.390/100 * 203.97304 = 2.835225256

2. 24.11/100 * 205.97447 = 49.660444717

3. 22.09/100 * 206.97590 = 45.72097631

4. 52.41/100 * 207.97665 = 109.000562265

We then add all of these masses together:

109.000562265 + 45.72097631+ 49.660444717 + 2.835225256 = 207.217208548

To 4 sf = 207.2 amu

Element is Lead (Pb)