Question

An element has three naturally occurring isotopes. Use the information below to calculate the weighted average atomic mass of the element, showing both the setup and the final answer for the calculation.

Isotope
Atomic Mass
Percent Abundance
A
15.99 u
99.762%
B
16.99 u
0.038%
C
17.99 u
0.200%

Answer 1

Answer: The average atomic mass of the given element is 15.99438 u

Step-by-step explanation:

Isotope-A atomic mass = 15.99 u

Isotope-A fractional abundance = 99.762 % = 0.99762

Isotope-B atomic mass = 16.99 u

Isotope-B fractional abundance = 0.038 % = 0.00038

Isotope-C atomic mass = 17.99 u

Isotope-C fractional abundance = 0.200 % = 0.00200

Average atomic mass of an element :

=
`\sum`(Atomic mass of an isotope) × (respective percent abundance)

`15.99 u* 0.99762+16.99 u* 0.00038+17.99 u* 0.00200=15.99438 u`

The average atomic mass of the given element is 15.99438 u