Question

An element has two stable isotopes. One has a mass of 6.015 amu and is 7.59 abundant. The second has a mass of 7.016 amu and is 92.41 abundant what is the average mass of the element.

What is the average atomic mass of the element

Answer 1

For isotope 1 (lithium-6), atomic mass =
6.015
×
7.59
/
100
=
0.4565385
6.015×7.59/100=0.4565385
For lithium-7, atomic mass
=
7.016
×
92.41
/
100
=
6.4834856
=7.016×92.41/100=6.4834856
Average atomic mass of lithium
=
0.4565385
+
6.4834856
=
6.9400241
a
m
u
=0.4565385+6.4834856=6.9400241amu