Atomic mass is the weighted average mass of an atom of an element based on the relative natural abundance of that element’s isotopes. The mass number is a count of the total number of protons and neutrons in an atom’s nucleus.

The relative atomic mass of an element is defined as the weight in grams of the number of atoms of the element contained in 12.00 g of carbon-12. To calculate the relative atomic mass of chlorine, the average mass of one atom of chlorine is found by considering 100 atoms of chlorine.

noun. the ratio of the average mass per atom of the naturally occurring form of an element to one-twelfth the mass of an atom of carbon-12Symbol: A r Abbreviation: r.a.m. Former name: atomic weight.

A relative atomic mass (also called atomic weight; symbol: Ar) is a measure of how heavy atoms are. It is the ratio of the average mass per atom of an element from a given sample to 1/12 the mass of a carbon-12 atom.

Relative and average atomic mass both describe properties of an element related to its different isotopes. However, relative atomic mass is a standardized number that’s assumed to be correct under most circumstances, while average atomic mass is only true for a specific sample.

Absolute mass or Actual atomic mass: Thus by multiplying the relative atomic mass with 1.6605 × 10-24g we can get the absolute or actual mass of an atom. Example (1) Find the absolute mass oxygen (O).

Relative mass in the average atomic mass of all the isotopes present in percentage while absolute mass is the sum of number of protons and neutrons mass. For example the absolute mass of carbon is 12.0 amu while 12.01 is the average atomic mass of carbon on the basis of percentage of C-12, C-13 and C-14 isotopes.

16 amu