How can an average atomic mass be calculated?

1 Answer
anor277
May 25, 2018

The average atomic mass, the mass quoted on the Periodic Table, is the WEIGHTED average of the individual isotopes...

Explanation:

Let's take a pertinent example... All chlorine in the universe so far as we know, is #75.8%# #""^35Cl# and #24.2%# #""^37Cl#...and to get the average atomic mass, we sum appropriately...

#{75.8%xx35+24.2%xx37}*"amu"#

#=35.5*"amu"#

And if you look at the Periodic Table beside you now, you find that it lists the atomic mass of chlorine as #35.5*g*mol^-1#. Capisce?

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