Question

A sample of sodium has a relative abundance of 75% with a mass number of 23, a relative abundance of 20% with a mass number of 22 and a relative abundance of 5% with a mass number of 24. What is the average atomic mass?

Answer 1

The average atomic mass of Sodium : 22.85

Further explanation

The elements in nature have several types of isotopes

Isotopes are atoms whose no-atom has the same number of protons while still having a different number of neutrons.

So Isotopes are elements that have the same Atomic Number (Proton)

Atomic mass is the average atomic mass of all its isotopes

Mass atom X = mass isotope 1 . % + mass isotope 2.% + ....

isotope 1 : 75%, mass number = 23

Isotope 2 : 20%, mass number = 22

Isotope 3 : 5%, mass number = 24

The average atomic mass :

`\tt avg~atomic~mass=0.75* 23+0.2* 22+0.05* 24\\\\avg~atomic~mass=17.25+4.4+1.2\\\\avg~atomic~mass=22.85`