Calculating Relative Atomic Mass (Ar)

This section will better explain the importance weighted average.

Earlier you learned that Cl35 is more abundant in nature than Cl37 because out of all the naturally occurring chlorine atoms, Cl35 is 75%. So, 75% and 25% are the percentage abundance of the two isotopes of chlorine.

Now, let’s calculate the Ar of chlorine using their masses and relative abundance.