2.  To describe an isotope
 To explain how atomic mass can vary within
one element
 To calculate the abundance of different
isotopes

3.  An element is usually defined by the number
of protons in the nucleus
 If the number of protons changes the element
changes
 The number of protons is equal to the
number of electrons in an atom
 However the number of neutrons can change
between different atoms of the same element

4.  An isotope is a chemical with a different
atomic mass but the same number of protons
as another
 Take carbon as an example

5.  The atomic mass of carbon on the periodic
table is 12.011
 This is the mean mass of carbon on Earth

6.  To calculate the abundance of one isotope it
is important to know the mass of all isotopes
and the mass on the periodic table
 We are going to calculate the % abundance of
carbon 12

7. It is firstly important to understand the concept
of proportions and percentages
Carbon 12 + carbon 14 = 100% of all carbon
We are trying to find the % of 12C so we will call
that x
This means that:
12x + (100-x)14 / 100= 12.011
where x is % carbon 12,
(100-x) is % carbon 14

8. 12x + (100-x)14/100 = 12.011
Multiply out the brackets
12x + 1400-14x /100= 12.011
Multiply by 100 to remove the /100
12x +1400 -14x = 1201.1
Subtract the whole number leaving only x on one side
12x – 14x = -198.9
-2x=-198.9
-x = 99.45
x = 99.45

9.  Research to find an element that has 2
common isotopes
 Calculate the relative abundances of these 2
isotopes – If you find a website that offers
you the information ensure that it is the
correct answer!
 Write out an exam style question and give it
to your neighbour

10. Average atomic mass =
(abundance of isotope 1)(mass of isotope 1) +
(abundance of isotope 2)(mass of isotope 2)

11. Isotope Isotopic mass (u) Isotopic abundance (%)
24Mg 24 78.99
25Mg 25 10.00
26Mg 26 11.01

12. (24)(0.7899)+(25)(0.10)+(16)(0.1101)=
18.9576 + 2.5 + 2.8626 =
24.3202

13.  You will be given an element from the
periodic table
 You will produce a short (3-4 minute)
presentation about that element
 The presentation MUST include the electronic
structure, isotopes of the element, symbol
and position on the periodic table
 It should also include uses of the element,
how it was discovered, impact of uses of the
element (if applicable)

14.  The student explains how science is applied and
how it may be used to address a specific problem
or issue in a local or global context.
 The student discusses the effectiveness of
science and its application in solving the problem
or issue.
 The student discusses and evaluates the
implications of the use and application of science
interacting with at least two of the following
factors: moral, ethical, social, economic, political,
cultural and environmental.

15.  The student uses sufficient scientific
language correctly.
 The student communicates scientific
information effectively.
 When appropriate to the task, the student
fully documents sources of information
correctly.