The element x has three naturally occurring isotopes. the masses (amu) and % abundances of the isotopes are given in the table below. the average atomic mass of the element is amu.

220.42098 amu

Explanation:

(220 .9 X  .7422) + (220 X .0.1278) + (218.1 X 0.13) =     220.42098 amu

These are weighted averages.

So, we will take mass of one and multiply by abundance percentage that is provided and add them together.

In order to calculate the  average atomic mass, we have to convert the percentages of abundance to decimals. So, you get

(220 .9 X  .7422) + (220 X .0.1278) + (218.1 X 0.13) =     220.42098 amu

6.4 cm (max) - 25 cm (min)