Average atomic mass - 1 | The Periodic Table and Atoms

Magnesium has 3 natural isotopes:

24Mg (78.990%) ⇒ isotopic mass = 23.985 amu

25Mg (10.000%) ⇒ isotopic mass = 24.986 amu

26Mg (11.010%) ⇒ isotopic mass = 25.983 amu

 

Calculate the average atomic mass of naturally occurring magnesium.

Average atomic mass = sum of the masses of the isotopes, each multiplied by its natural abundance

Average atomic mass = 23.985 x 0.78990 + 24.986 x 0.10000 + 25.983 x 0.11010 = 24.305 amu