At least two people have tried to show you the light as to where your error is and instead of taking two minutes to research (I gave you the hint ... Google Chlorine atomic weight) that will back up our facts as presented to you and what do you do? You make some outrageous attack. I really hope that you reconsider your position, fix your attitude, do the research and come back and acknowledge your error. I don't expect you to apologize for the above snip but it would be refreshing.
*Sigh*
“You make some outrageous attack”
And you are being sweetness and light? Great, solid attitude here.
Relative atomic mass is not an intrinsic elemental property. It’s misleading. It assumes experimentally derived information which may or may not be the case with the actual sample.
It’s not universally applicable, and there are many applications for which it is not useful at all. This is why periodic tables should state the mass of the most common isotope which is true no matter what sample you use or how you go about doing things. Why? Because it’s related to the intrinsic characteristics of the element, the neutrons, protons and electrons. It’s not reliant upon ‘expected ratio in nature’, which isn’t always the case.