There are only two isotopes of bromine on earth: bromine-79 and bromine-81. By looking at the periodic table. What can you tell about bromine?

Question

a. Bromine-79 and Bromine-81 atoms combine to create bromine-80. b. Half of the bromine on earth is bromine-79 c. There is about the same amount of both bromine-79 and -81 on earth

Answer 1

The atomic mass of bromine is 79.90, which is less than 80, the average of 79 and 81.

This will tell you that there are slightly more bromine-79 than bromine-81 among the bromine isotopes that have been found so far.

The best choice is c.

 

If you want to find the % of each bromine isotope, just solve the following equation for x.

 

Let x be the fraction of bromine which are bromine-79 isotopes, then  1-x will be fraction of bromine that are bromine-81 isotopes.

 

79x + 81(1-x) = 79.90

 

I let you have fun calculating x.  (x should be > 0.5)