The element thallium is 70% thallium-205 and 30% thallium-203. calculate its relative atomic mass. give your answer to 4 significant figures

General
1

the element thallium is 70% thallium-205 and 30% thallium-203. calculate its relative atomic mass. give your answer to 4 significant figures.

2

LectureNotes said the element thallium is 70% thallium-205 and 30% thallium-203. Calculate its relative atomic mass. Give your answer to 4 significant figures.

Answer: To calculate the relative atomic mass of thallium, given that it consists of 70% thallium-205 and 30% thallium-203, we will use the concept of weighted average. The relative atomic mass can be calculated using the following formula:

\text{Relative Atomic Mass} = (\text{Fraction of Isotope 1} \times \text{Mass of Isotope 1}) + (\text{Fraction of Isotope 2} \times \text{Mass of Isotope 2})

Given:

  • Thallium-205 makes up 70% (or 0.70) of the element.
  • Thallium-203 makes up 30% (or 0.30) of the element.
  • The mass of Thallium-205 is 205 atomic mass units (u).
  • The mass of Thallium-203 is 203 atomic mass units (u).

Let’s plug these values into the formula:

\text{Relative Atomic Mass} = (0.70 \times 205) + (0.30 \times 203)

Calculate each term separately:

  • For Thallium-205: 0.70 \times 205 = 143.5
  • For Thallium-203: 0.30 \times 203 = 60.9

Add these values together to get the relative atomic mass:

\text{Relative Atomic Mass} = 143.5 + 60.9 = 204.4

Therefore, the relative atomic mass of thallium, to four significant figures, is 204.4.