Naturally occurring thallium consists of two stable isotopes, Tl-203 and Tl-205 (atomic masses = 203.0 and 205.0, respectively) and has an average atomic mass of 204.4. What is the percentage of Tl-205?

Expert Answers

An illustration of the letter 'A' in a speech bubbles

Let us say we have `X%` of Ti-205. Then the rest `(100-X)%` is the Ti-203 percentage.

It is given that average atomic mass of Ti is 204.4.
Mass of Ti-205 in isotope` = X/100xx205`

Mass of Ti-203 in isotope `= (100-X)/100xx203`

`X/100xx205+(100-X)/100xx203 = 204.4`

`205X+20300-203X = 20440`

`X = 70`

So the percentage of Ti-205 in the isotope is 70%.

See eNotes Ad-Free

Start your 48-hour free trial to get access to more than 30,000 additional guides and more than 350,000 Homework Help questions answered by our experts.

Get 48 Hours Free Access
Approved by eNotes Editorial Team