8. Various ways of identifying
Isotopes
• Using atomic notation,
Example: 12
6 C or simply 12 C
•Using the mass notation.
Example: Carbon-12 or C-12
(read “carbon twelve” or “C twelve”)
9. Some Isotopes of Carbon
mass
notation
atomic
notation
# of p+ # of e- # of no
C-11 11C 6 6
C-12 12C 6 6
C-13 13C 6 6
C-14 14C 6 6
11. The Isotopes of Hydrogen
mass
notation
atomic
notation
# of p+ # of e- # of no
Hydrogen-1 1H 1 1
Hydrogen-2 2H 1 1
Hydrogen-3 3H 1 1
12. p+ =
no =
e- =
p+ =
no =
e- =
p+ =
no =
e- =
Figure #1 Figure #2 Figure #3
13. Isotopes
atoms of a given element that
differ in the number of neutrons
…and consequently in mass.
14. Why are masses on the periodic
table usually expressed as decimal
numbers?
• masses on the table are weighted
averages of all known isotopes of
the element of interest
15. Keep in mind:
It is not possible to determine how many
different isotopes exist by looking at the
periodic table.
It is not possible to determine the
frequency of various nuclides by looking
at the periodic table.
16. The following does not occur in nature!
1
1H occurrence 33.3%
2
1H occurrence 33.3%
3
1H occurrence 33.3%
17. The following does occur in nature!
1
1H occurrence 99.98%
2
1H occurrence 0.0156%
3
1H occurrence 0.0044%
18. another way of looking at it:
1
1H occurrence 9,998
2
1H occurrence 1.56
3
1H occurrence 0.44
Imagine having 10,000 H atoms
19. That means the weighted average is:
1
1H 1 x 0.9998 = 0.9998
2
1H 2 x 0.00156 = 0.00312
3
1H 3 x 0.00004 = 0.00012
Weighted Average (0.9998 + 0.00312 + 0.00012) 1.01
23. (parenthesis) on the
Periodic Table indicate the
most stable isotope
stable means “longest living”
Parenthesis also suggest the element of
interest is radioactive.
26. Review problem #3
If the atom described below had 2 naturally occurring
isotopes, which of the 2 would have a greater
frequency of occurrence? Express your answer in
atomic and mass notation.
3
Li
Lithium
6.941
27. Review problem #4
How many total subatomic particles are in the following
“neutral” atoms of Fe-55 and Fe-57?
