The document provides an overview of atomic structure, focusing on subatomic particles, atomic numbers, and isotopes. It explains that the atomic number identifies elements by the number of protons in the nucleus, while isotopes are variants of elements with the same number of protons but different neutrons. It also discusses the calculation of relative atomic mass, considering the abundance of isotopes.

1. Atomic
Number,
Atomic Mass,

2. Proton
Neutro
n
Electro
n
So far you have
learned about the
different subatomic
particles of an atom.
REVIEW

3. Proton
It is the number of protons
that identify the atoms of an
element.
Number of
protons
Remember: All atoms in an
element contain the same
number of protons in their
nuclei.

4. -is the number of protons, and therefore also
the total positive charge, in the atomic nucleus.
Atomic Number
Each element has their respective atomic
number.

5. Key Learning
Points
Locate the atomic number in the
periodic table.
Identify the subatomic particles
associated with mass number
Determine the number of neutrons
from the mass number
Define isotope

6. Atomic
Number
Z
This is the number of units of positive charge in
the nucleus.

7. Atomic
Mass
A
Mass
Number
Atomic
Weight

8. Proto
n Neutron
0
n
Electron
p+
-
e

9. -
e
Z=p+=

10. A =p++ 0
n
-
e
= + 0
n
= Z + 0
n

11. 0
n =A-p+
=A -
e
=A-Z
-

12. Element
Z A
Atomic
Weight
p+ -
e 0
n
Au
Al
U
79
13
79 197
238 92
14

14. Proton
Neutro
n
Electro
n
Isotopes are atoms of
the same element
with different
numbers of neutrons
(they have the same
number of protons).
What are
isotopes?

15. There are three isotopes
of hydrogen. All
hydrogen atoms contain
one proton (and one
electron), but they can
have different numbers
of neutrons. Hydrogen-1
Hydrog
en-1
Hydrog
en-2
Hydrog
en-3
Example
1

16. There are two isotopes of chlorine.
All chlorine atoms contain
seventeen protons (and seventeen
electrons), but they can have
different numbers of neutrons.
Chlorine-35 is the most commonly
Example
2

17. Isotopes have the same
chemical properties. This
is because the number of
electrons determines
chemical properties,
isotopes have the same
number of electrons in
Propertie
s

18. The relative atomic mass of
an element in the periodic
table, is the weighted
average of the masses of
the atoms of the isotopes.
Relative atomic mass takes
into account the abundance
of each of the isotopes of
The relative atomic mass
of chlorine is 35.45 rather
than a whole number.
This is due to chlorine
having two isotopes
(chlorine-35 and chlorine-
Relative Atomic
Mass

19. Copper has two isotopes:
• Copper-63 which accounts for
69% of copper
• Copper-65 which accounts for
31% of copper
Calculate the relative atomic mass
of copper to one decimal place.
Calculating the Relative Atomic
Mass
Questio
n
(69 X 63) + (31 X
65) = 6362
6362 / 100 = 63.6
Answe
r

20. Isotopes
Atomic Structure & the
Periodic Table

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