[SeeSac]

Take it up with the IUPAC. I am done with you and your refusal to go google Chlorine.

The IUPAC definition of atomic weight is:

An atomic weight (relative atomic mass) of an element from a specified source is the ratio of the average mass per atom of the element to 1/12 of the mass of an atom of 12C.

[BenKenobi]

“An atomic weight (relative atomic mass) of an element from a specified source is the ratio of the “average mass per atom of the element to 1/12 of the mass of an atom of 12C.”

Which is not the definition that you are using here.

Thank you for quoting this.