Question

Thallium has two isotopes thallium-203 and thallium-205 find which isotope is more abundant\abundance

Answer 1

Let we have X of Tl-205 so the percent of Tl-203 will be 100-X

Average mass of Thallium is 204.4

Mass of Tl-205=
`(X* 205)/(100)`

Mass of Tl-203=
`(100-X* 203)/(100)`

So,

`(100-X* 203)/(100)+(X* 205)/(100)=204.4`

205X +20300-203X=20440

X=70

So the percent or abundance of Tl-205 is 70 while that of Tl-203 will be 30.