Question

Given the relative abundance of the following naturally occurring isotopes of oxygen, calculate the average atomic mass of oxygen:
Oxygen-16: 99.76%
Oxygen-17: 0.037%
Oxygen-18: 0.204%

Answer 1

Answer:

The average atomic mass of oxygen is 16 a.m.u

Explanation:

The atomic mass (A) is obtained by adding the number of protons and neutrons in a given nucleus.

The same chemical element can be made up of different atoms, that is, atoms where the number of neutrons is different. These atoms are called isotopes of the element.

The atomic mass of an element is the weighted average mass of its natural isotopes. Therefore, the atomic mass of an element is not an integer. The weighted average means that not all isotopes have the same percentage. In other words, the atomic masses of the chemical elements are usually calculated as the weighted average of the masses of the different isotopes of each element taking into account the relative abundance of each of them:

average atomic mass=Σ(isotope mass*percent abundance)

So in this case:

average atomic mass= 16 a.m.u*0.9976 + 17 a.m.u*0.00037 + 18 a.m.u*0.00204

average atomic mass= 16 a.m.u

Answer 2

The average atomic mass of oxygen is 16 amu.

According to the formula of average atomic mass of oxygen

= $\frac{Sum of (Mass of each isotope)(relative abundance)}{100} \\\\= \frac{((16)(99.76)+(17)(0.037)+(18)(0.204)}{100} \\\\=16 amu$