Chemistry 20 – Atoms & Elements
2-2
Understanding Isotopes
References:
Section 6-17 (Quarks)
Section 6-19 (Mass Number)
Section 6-21 (Determining Atomic Masses from Weighted Averages)
SmartBoard Notes: 2-2 Parts of Atom
Section A - Main Concepts:
12
13
14
1. Here are three isotopes of an element:
6 C
6 C
6 C
a) The element is: __________________
b) The number 6 refers to the _________________________
c) The numbers 12, 13, and 14 refer to the ________________________
d) How many protons and neutrons are in the first isotope? _________________
e) How many protons and neutrons are in the second isotope? _________________
f) How many protons and neutrons are in the third isotope? _________________
g) Complete the following:
• Isotopes are atoms of the same _________________ (shown by the atomic
number) which has a different number of _____________ and
_____________ (shown by the mass number).
2. Complete the following chart for the elements listed.
Isotope
# of Protons # of Neutrons
Atomic #
Oxygen-16
Mass #
Symbol
Oxygen-18
Fluorine-18
Fluorine-19
P-31
P-32
P-33
7
4
18
4
17
24
12
Mg-25
12
26
7
22
S-34
17
19
28
Al
Fe-59
3. What is a quark? What are the 6 types of quarks? What other ‘simpler particles’ (like quarks)
do scientists believe exist?
4. Naturally occurring europium (Eu) consists of two isotopes was a mass of 151 and 153.
Europium-151 has an abundance of 48.03% and Europium-153 has an abundance of 51.97%.
What is the atomic mass of europium?
5. Magnesium occurs in natural form as a mixture of 3 different isotopes, as described below:
Isotope
Abundance
Atomic Mass
Mg-24
78.70%
23.985
Mg-25
10.13%
24.986
Mg-26
11.17%
25.983
Using this data, determine the relative (average) atomic mass that scientists have determined
for Magnesium.
Section B – Applications:
Choose 1 of the following topics, and use Microsoft Publisher to create a 11x17 poster.
1. You have been hired by the Dow Chemical Company to market the importance of isotopes.
Choose one of the following, and create a marketable poster which highlights the uses (with
chemical properties and physical properties), benefits/drawbacks, and ‘chemical details’ we
learned in class (mass number, atomic number), along with a chemical picture of the isotope
similar to the following:
Your choices:
a) Isotopes in carbon dating
b) Isotopes in surface and groundwater investigations
c) Isotopes in nutrition
d) Medical isotopes used in diagnosis
e) Medical isotopes used in treatment of disease
f) Isotopic labelling in chemical reactions
g) Isotopes in pest control
h) Isotopes used in agriculture
i) Isotopes in climatology and geology
j) Isotopes in nuclear weapons testing
k) Isotope use in smoke alarms
l) Isotopes in biological tracing
2. People in the area are worried that too much radiation will create a problem like what
happened in Chernobyl, Ukraine. Three of the isotopes that affected countries around Ukraine
were Cesium-137, Iodine-131, and Strontium-90. Health Canada wants you to prepare a poster
which details the health effects of each of these isotopes.