Question

Thallium consists of 29.5%Th-203 and 70.5%Th-205. What is the relative atomic mass of thallium?

Answer 1

0.295 * 203 = 53.885
0.705 * 205 = 144.525
53.885 + 144.525 = 204.41
The relative atomic mass of Thallium is 204.41 

Answer 2

Answer:

204.41 is the relative atomic mass of thallium.

Explanation:

Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

$\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i$ .....(1)

We are given:

Mass of Thallium-203= 203 u

Percentage abundance of Thallium-203= 29.5%

Fractional abundance of Thallium-203= 0.295

Mass of Thallium-205 = 270.9 u

Percentage abundance of Thallium-205 = 70.5%

Fractional abundance of Thallium-203 = 0.705

Putting values in equation 1, we get:

$\text{Average atomic mass of Thallium}=\sum[(203 u\times 0.295)+(205 u\times 0.705)]$

$\text{Average atomic mass of Thallium}=204.41 u$

204.41 is the relative atomic mass of thallium.