3. Famous Scientist John
Dalton had assumed that
all atoms of the same
element had identical
masses.
Frederick Soddy
proposed the isotope
concept—that elements
could have more than one
atomic weight. Credit: University of Glasgow Archive Services,
GB0248 UP1/503/1
Soddy in his lab at the University of Glasgow
BACKGROUND
4. ISOTOPES
The word isotope was derived from Greek
words isos and topos which means “the same
place”.
Isotopes variants of an element are still found
in the same location in the periodic table of
elements.
This term was introduced by a British Chemist
Frederick Soddy.
5. ISOTOPES
Isotopes are atoms of the same element that
have the same number of protons but different
in the number of neutrons.
6. Working with Atomic Notation
A
zX
Atomic Number
Chemical Symbol
Atomic Mass
(of Isotope)
11. 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”)
12. 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
14. p+ =
no =
e- =
p+ =
no =
e- =
p+ =
no =
e- =
Figure #1 Figure #2 Figure #3
15. 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
16.
17.
18. An element with three stable isotopes has
82 protons. The separate isotopes contain
124, 125 and 126 neutrons. Identify the
element and write symbols for isotopes.
19. Identify the element with 35 protons. write
symbols for its isotopes with 44 and 46
neutrons.
20.
21. Relative atomic mass= mass
number of each isotope x %
abundance of each isotope in
decimal form
The relative atomic mas of atoms
are reported using the atomic mass
unit(amu)
23. Chlorine-35 makes up 75.53 percent of all the chlorine in
nature, and Chlorine-37 makes up the other 24.47 percent.
The relative atomic mass of chlorine is calculated as
follows;
24. Problem Solving
Oxygen has three isotopes, Oxygen- 16, Oxygen- 17 and Oxygen- 18, whose
percentage abundances are 99.757%, 0.0378% and 0.205% respectively.
The atomic masses of Oxygen-16, Oxygen-17 and Oxygen-18 are 15.994915
amu , 16.999132 amu and 17. 999161 amu respectively. Write the symbols
for the three isotopes of oxygen and determine the relative atomic mass.
25.
26.
27. Problem Solving
Elemental Bromine is made up of two naturally occurring isotopes Br-79 and
Br -81 which have an atomic mass of 78.918 amu and 80. 916 amu
respectively . The average atomic mass of Bromine is 79.9 . Calculate the
Percent abundance of each Isotope.
28. Problem Solving
Nitrogen is made up of two isotopes, N-14 and N-15.
Given the nitrogen’s atomic weight of 14.007, what is the
percentage abundance of each isotope?
29.
30. Problem Solving
1. Boron has two isotopes, Boron-10 and Boron-11, whose percentage
abundances are 19.8% and 80.2% respectively. The atomic masses of
Boron-10 and Boron-11 are 10.0129 amu and 11.0093 amu respectively.
Write the symbols for the two isotopes of boron and determine the relative
atomic mass.
31. Problem Solving
2. Silicon has three isotopes, Silicon-28, Silicon-29 and Silicon-30, whose
percentage abundances are 92.21%, 4.70% and 3.09% respectively. The
atomic masses are 27.977 amu, 28.976 amu and 29.974amu respectively.
Write the symbols for the three isotopes of silicon and determine the
relative atomic mass.
32. Problem Solving
3. Iron has four isotopes, Iron- 54, Iron- 56, Iron- 57 and Iron- 58, whose
percentage abundances are 5.82%, 91.66%, 2.19% and 0.33%
respectively. The atomic masses are 53.9396611 amu, 55.934938 amu
56.935394 amu and 57.933276 amu respectively. Write the symbols for
the four isotopes of Iron and determine the relative atomic mass.
33. Problem Solving
4. Uranium has three isotopes, Uranium- 234, Uranium- 235 and Uranium-
238, whose percentage abundances are 0.0054%, 0.7204% and 99.274%
respectively. The atomic masses are 234.040952 amu, 235.043930 amu
and 238.050788 amu respectively. Write the symbols for the three isotopes
of uranium and determine the relative atomic mass.
34. Problem Solving
5. Boron has two naturally occurring isotopes , B-10 with an atomic mass of
10. 0129370 amu and B-11 with an atomic mass of 11.009306 amu. The
average atomic mass of boron is 10.811 amu. Calculate the percentage of
abundance for each isotope.
35. Problem Solving
6. A naturally occurring Bromine consist of two isotopes, Br-79 and Br-81,
whose percentage abundances are 50.69% and 49. 31% respectively. The
atomic masses of Bromine- 79 and Bromine 81 are 78.9183 amu and
80.9163 amu respectively. Write the symbols for the two isotopes of bromine
and determine the relative atomic mass.
36. Problem Solving
7. Magnesium has three natural isotopes.Mg-24, Mg-25 and Mg-26, with
atomic masses of 23. 985042, 24. 985837and 25. 982593 amu
respectively. If the average atomic mass of magnesium is 24. 3050 amu
and 78.99% of all magnesium is Mg-24. what are the abundances of Mg-
25 and Mg-26?
40. isotopes Use/s
Sodium-24 Injected into limb to detect blood cloth
Cobalt-60 Detect and Treat Cancer/ use to kill bacteria
Iodine-131 Detect functions of Thyroid Gland
Phosphorous-32 Added to fertilizer to study plant processes
Nitrogen-15 Added to fertilizer to study plant processes
Cesium-137 Use to kill bacteria
Flourine-18 Use for diagnosis and treatment of diseases
Gallium-67 Use for diagnosis and treatment of diseases
Carbon-14 Carbon dating Process
41.
42.
43. Activity – Isotope Brochure
Procedure:
• 1. Choose an isotope that you want to discuss and
present it in a brochure format. Discuss the history,
applications in various fields like medicine,
agriculture, industries and health, as well as the
adverse effects.
• 2. Prepare 1 long special cardboard paper, pen,
cut-outs of the chosen isotopes and adhesive
material such as glue.
• 3. Fold the special cardboard paper into 3 then
make a lay out of your isotope brochure.
44.
45. Questions:
1. Which field is the chosen isotope most
useful?
2. Is there any adverse effect in using the
chosen isotope? How?
46. 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
50. (parenthesis) on the
Periodic Table indicate the
most stable isotope
stable means “longest living”
Parenthesis also suggest the element of
interest is radioactive.
54. Direction: Solve for what is being asked in the following problems:
1. Silver has two stable isotopes, Ag- 107 and Ag-109. Ag-107 has a mass of
106.90509 amu and Ag-109 has a mass of 108. 90476 amu. If the average
atomic mass of Silver is 107.8682. Calculate the percentage abundance of
each isotope.
1. Lithium has two isotopes, Li- 6 with an atomic mass of 6. 0151 and Li-7 with
an atomic mass of 7. 0160. The average atomic mass of Lithium is 6. 925
amu. Calculate the percentage abundances of each isotope.
1. A naturally occurring element of Carbon has three isotopes, C-12, C-13 and
C-14. If the average atomic mass of carbon is 12.01 amu and 98.9 % of all
Carbon is C-12. Calculate the abundances of C-13 and C-14.
