Sat August 20, 2011 By: Sajad Bhat

How to calculate exact atomic mass of a particular element eg. in case of Iodine (I) At. mass=126.9, as it is not the sum of masses of protons and its neutrons

Expert Reply
Tue August 23, 2011
The atomic weight of an element depends on the abundance of its isotopes. If you know the mass of the isotopes and the fractional abundance of the isotopes, you can calculate the element's atomic weight. The atomic weight is calculated by adding the mass of each isotope multiplied by its fractional abundance.
Average atomic mass = (fraction1 x atomic mass1) + (fraction2 x atomic mass2) + (fraction3 x atomic mass3) ...
Ask the Expert