Attempt 1
The element carbon has two naturally occurring isotopes. The isotopic masses and abundances of these isotopes are shown
in the table.
Isotope
12c
13C
Isotopic mass (u)
12.00
Abundance (%)
98.93
13.00
1.07

Calculate the average atomic mass of carbon to two digits after the decimal point.
average atomic mass =

The average atomic mass of carbon, made up of 2 naturally occurring isotopes, 12C and 13C, is 12.01 u.

The element carbon has two naturally occurring isotopes. 12C with an atomic mass of 12.00 u and an abundance of 98.93% and 13C with an atomic mass of 13.00 u and an abundance of 1.07%. We can find the average atomic mass (aam) of carbon, which is a weighted average that considers the mass of each isotope () and the abundance of each isotope () using the following expression.

The average atomic mass of carbon, made up of 2 naturally occurring isotopes, 12C and 13C, is 12.01 u.

You can learn more about average atomic mass here: link

12.01

Explanation:

(12.00*98.93% + 13*1.07%) /100% = 12.01