Question #a31cd

1 Answer
Aug 14, 2016

Those are mass numbers of each molecular isotope, meaning those of #"Br"_2#. Bromine is naturally a diatomic liquid.

It doesn't mean that there are three naturally-existing atomic isotopes, but it does mean that one #"Br"# on #"Br"_2# doesn't necessarily have to be #""_(35)^(81) "Br"# if the other is #""_(35)^(81) "Br"#, for example.

Add up the mass numbers and you should see that:

#79 + 79 = color(green)(158)#
#79 + 81 = color(green)(160)#
#81 + 81 = color(green)(162)#

That means you have the three naturally-existing isotopic molecules:

#color(blue)(""_(35)^(79) "Br"-""_(35)^(79) "Br")#

#color(blue)(""_(35)^(79) "Br"-""_(35)^(81) "Br")#

#color(blue)(""_(35)^(81) "Br"-""_(35)^(81) "Br")#

Therefore, you still have:

  • Two naturally-existing atomic isotopes.
  • Due to the diatomic nature of naturally-existing bromine liquid, three combinations of atoms are possible, generating three naturally-existing molecules containing the three different combinations of atomic isotopes.