Are atomic mass and atomic weight the same thing?

1 Answer
Jan 15, 2016

No, they are not the same thing.

Explanation:

An atomic weight (or relative atomic mass) is the ratio of the average mass of all the isotopes of an element to 1/12112 of the mass of an atom of ""^12"C"12C.

Hence an atomic weight has no dimensions.

Atomic mass is the mass of a neutral atom of a specific isotope.

The SI unit for atomic mass is the unified atomic mass unit (u), which is defined as 1/12112 of the mass of an atom of ""^12"C"12C.

Thus, the atomic weight of "C"C is 12.011, but the atomic mass of ""^12"C"12C is 12 u.