Take 234/100 x 0.01
then 235/100 x 0.71
then 238/100 x 99.28
you divide by 100 because the abundance is given in percentage over 100
then add up all the values, you should get an answer of 237.97 rounded up is 238.
Final answer : 238
hope this helped :)
Explanation:
Calcium chloride is an ionic compound as it is formed by transfer of an electron to each chlorine atom.
So, being an ionic compound calcium chloride is able to dissociate completely into water.
Hence, the dissociation reaction will be as follows.

Since, two electrons has been lost by single calcium atom. Therefore, calcium atom will have a charge of +2.
Thus, we can conclude that the charge on the calcium ion, in elementary units is +2.