Name: _________________________________________ Date: ______________ Block: _____
Isotopes and average atomic mass practice problems
Here are three isotopes of an element: 12C
1) The name of the element is:
13
14
C
C
___________________
2) The numbers 12, 13, and 14 refer to the ________________
3) Complete the table below:
Atomic Atomic
symbol
#
12
C
13
C
14
C
Mass
#
# of
# of
# of
protons neutrons electrons
4) Naturally occurring europium (Eu) consists of two isotopes was
a mass of 151 and 153. 151Eu has an abundance of 48.03% and
153
Eu has a relative abundance of 51.97%. What is the atomic
mass of europium?
5) Strontium consists of four isotopes with masses of 84
(abundance 0.50%), 86 (abundance of 9.9%), 87 (abundance of
7.0%), and 88 (abundance of 82.6%). Calculate the atomic mass
of strontium.
6) Rubidium is a soft, silvery-white metal that has two common
isotopes,
85
Rb and
87
87
Rb. If the abundance of
85
Rb is 72.2% and
the abundance of Rb is 27.8%, what is the average atomic
mass of rubidium?
7) Uranium is used in nuclear reactors and is a rare element on
earth. Uranium has three common isotopes. If the abundance
of
234
U is 0.01%, the abundance of
abundance of
of uranium?
235
238
U is 99.28%, what is the average atomic mass
8) Titanium has five common isotopes:
48
U is 0.71%, and the
46
Ti (8.0%),
47
Ti (7.8%),
Ti (73.4%),
49
Ti (5.5%), 50Ti (5.3%). What is the average atomic mass of
titanium?
9) Why is the mass in amu of a carbon-12 atom reported as 12.011
in the periodic table of the elements?