Isotopes
Show your work
1. How many protons, electrons, and neutrons make up an atom of
Protons: _________ Electrons: _________ Neutrons: _________
bromine-80?
2. Calculate the average atomic mass of boron from the following information:
Isotope
% Abundance
Atomic Mass
10
B
18.8
10.0
11
B
81.2
11.0
Average atomic mass: _________________
3. Calculate the average atomic mass of element X in which isotope one (42.00%)
weighs 138.2 amu and its second isotope (58.00%) weighs 151.6 amu.
Average atomic mass:__________________
4. Calculate the average atomic mass of element Z in which the first isotope found in
28.5% abundance weighs 200.0 amu and the other isotope weighs 220.0 amu.
Average atomic mass: __________________
5. Antimony has two common isotopes. If one of the isotopes is antimony-121 with an
atomic mass of 120.9038 amu and an abundance of 57.25%, what is the atomic mass (to
4 significant figures) of the second isotope? The average atomic mass of antimony is
121.75.
Atomic mass of second isotope: ___________