Students’ copy
Chapter 8:
Atoms & Molecules
Theme: Models
Duration: Express~12 periods, NA~9 periods
Students’ copy
Learning objectives
At the end of the lesson, you should be able to:
1.
compare the size of an atom with the sizes of everyday objects [POS]
2.
*show an appreciation of how, in practice, models are constructed, justified and continuously
revised as they are used to probe new phenomena and collect additional data (e.g., the various
atomic models) [VEA]
3.
describe an atom as an entity that is electrically neutral and is made up of a positively charged
nucleus (protons and neutrons) with negatively charged electrons moving around the nucleus [CI]
4.
*recognise that atoms have mass that is mainly contributed by the mass of the nucleus [CI]
5.
show an awareness that the atoms of an element have a unique number of protons [CI]
* Optional for N(A) Science
Students’ copy
Learning objectives
At the end of the lesson, you should be able to:
6.
compare atoms and molecules [POS]
7.
show an understanding that a molecule is a group of two or more atoms that are chemically
combined [CI]
8.
state the numbers and types of atoms, given the chemical symbol of an element or the chemical
formula of a compound, e.g., carbon dioxide (Note: Writing of chemical formulae is not required.
Giant molecular compounds are also not required.) [CI]
9.
show an awareness that technologies resulting from the knowledge of atoms have created social
and ethical issues, risks and costs (e.g., atomic bombs) [VEA]
8.1
What is the simplest unit of an element
and how do we represent its structure?
AB 8.1.1: How small is an Atom?
AB Page: 91, 93
*Not doing the practical,
Watch video on the next slide and attempt Q2 on page 93
Go through in class: 15 min
8.1
What is the simplest unit of an element
and how do we represent its structure?
AB 8.1.3: Why is an Atom Electrically Neutral?
AB Page: 101 - 103
Duration: 60 min (2 periods)
Teachers’ Notes: The SLS package is titled “Why Is an Atom
Electrically Neutral? [LSS (Exp/NA)]”.
8.1
What is the simplest unit of an element
and how do we represent its structure?
AB 8.1.4: What makes up the Mass of an Atom?
AB Page: 105
(*Optional for NA)
Go through in Class: 15 min
8.1
What is the simplest unit of an
element and how do we
represent its structure?
Read textbook page 64 – 71
8.1
What is the simplest unit of an
element and how do we
represent its structure?
Duration: 15 mins
(1)Introduction to atom
• All matter is made up of tiny invisible
particles called atoms
Definition of an atom
•
An atom is defined as the
smallest particle of an element
characterizing the element
that can exist
All elements in the
Periodic Table are made
up of atoms
E.g. Gold is an element which is
made up of gold atoms (the
smallest particles in gold). It is
these particles that determines
the properties of gold.
How small are atoms?
Most part of an atom is empty space. If the size of
an atom were the size of a football field, the size
of nucleus would be like the size of a pea!
pea
Atoms are made of sub-atomic particles called
electrons
neutrons and ___________.
protons __________
___________,
(2) Nature of the Sub-atomic particles in an atom
The Three Main Sub-atomic Particles
• Protons and neutrons are in the nucleus
• Electrons are found in electron shells found away from the nucleus.
16
Sub-atomic Particle
Relative Mass
Relative Charge
Location in the Atom
proton
1
+1
nucleus
neutron
1
0
nucleus
electron
1
1840
–1
around the nucleus on
electron shell
(3) Atoms are Electrically Neutral
• Atoms are electrically neutral.
• Number of protons = number of electrons
17
(4) Number of Neutrons in an Atom
• Unless the number of electrons, the number of neutrons in an atom is not always
equal to the number of protons in the atom.
18
© 2023 Marshall Cavendish Education Pte Ltd
(5) Mass of an Atom
• Mass of an atom is mainly contributed by the mass of the protons and neutrons
in the nucleus.
• Electrons have mass, but they are much lighter compared to protons and
neutrons. Thus, mass of electrons is considered negligible and does not add up to
the mass of the atom.
19
Type of Atom
Number of
Protons
Number of
Electrons
Number of
Neutrons
Atomic Mass
(mass of Protons +
Neutrons)
Hydrogen
1
1
0
1
Helium
2
2
2
4
Lithium
3
3
4
7
Potassium
19
19
20
39
© 2023 Marshall Cavendish Education Pte Ltd
8.2
How can the number of
Protons in an Atom be used to
identify an Element?
Read textbook page 72 - 74 &
notes in the subsequent slides
Classifying Elements – The Periodic Table
• At present, there are 118 known elements.
• They are represented by chemical symbols and grouped in a
table called the Periodic Table of elements.
Classifying Elements – The Periodic Table
The elements are arranged in
increasing proton number
Across the Periodic Table, from left
to right, the proton number
increases by 1.
Classifying Elements – The Periodic Table
Dividing line separates the
metals
non-metals
and non-metals
metals
Elements such as silicon and
germanium, found close to
the dividing line are known
as metalloids.
Metalloids exhibit some
properties of metal and nonmetals.
Classifying Elements – The Periodic Table
Vertical columns are called Groups.
Total = 18 groups Labelled as Group
1,2,3,…,18
Classifying Elements – The Periodic Table
Horizontal rows are called Periods.
Total = 7 Periods. Labelled as 1, 2, 3..
Classifying Elements – The Periodic Table
Representing Elements
Each element in the Periodic Table are represented in the following
format:
11
proton (atomic)number
6
Na
C
sodium
atomic symbol
element name
23
relative atomic mass
carbon
12
• Each element is given a proton number which is unique to the element
(just like your NRIC number).
• For elements represented by more than 1 letter, the 1st letter of the
atomic symbol must be a capital letter and the subsequent letters are
small letters
8.2
How can the number of Protons in an
Atom be used to identify an Element?
AB 8.2.1: Are they from the same Element?
AB Page: 107 - 108
Go through in class: 30 min (1 period)
8.3
How do we represent the Simplest Units
of Elements and some Compounds?
AB 8.3.1: What are Elements & Compounds made
up of?
AB Page: 109 ñ 111
Go through in class: 60 min (2 periods)
8.3
How do we represent the Simplest
Units of Elements and some
Compounds?
Duration: 15 mins
Molecules
#wO
A molecule is made up of ……………………………..
or
more
……………………………..atoms
of the
same
……………………………..
element or
different
……………………………..
elements
……………………………..
combined together.
chemically
element
 A molecule of an ……………….
consists of only
………………. type of atoms that are chemically
ove
combined.
Oxygen – O2
O
Nitrogen – N2
Ozone– O3
O
N
O
N
O
O
 A molecule of a ………………… consists of two
more ………………….. types of atoms that are
chemically combined.
O
Nitrogen
dioxide – NO2
Water– H2O
H
N
O
O
H
Chemical Formula
 The chemical formula is another way to represent
molecules.
 A chemical formula provides two information of a
substance:
type
(a)The ………………….
of elements in the compound.
number
(b)The ………………….
of atoms in each element in the
compound.
Chemical Formula
• Examples:
Name
Formula
Element present
Number of each
element
Carbon dioxide
CO2
Carbon
Oxygen
1C
2O
O
C
O
Molecules of
compound
Zinc
InS
SUIfUr
aluminum
flOUrde
aluminium
scouvire
↑
AI
I
3
sodium
oxide
sodium
Na
2
oxygen
0
I
magnesium
hitrogen
oxygen
Mig
N
0
I
I
car
~
sulfuric
acid
bun
E
hydrogen
H
oxygen
0
hydrogen
sulfur
uxygen
2
↳
2
1
S
O
2
I
4
w
8.4
What are some Applications of Atomic
Technologies and the possible issues that
can arise from them?
Read TB 79 ñ 82
8.4
What are some Applications of Atomic
Technologies and the possible issues that
can arise from them?
AB 8.4.1: Issues related to the Applications of
Atomic Technologies
AB Page: 113 ñ 115
Go through in class: 60 min (2 periods)
Practice Questions
AB Page 117 ñ 118
Go through in class: 30 min (1 period)
(20 marks)
Duration: 25 min (1 period)
(Optional for NA)
7 Model of Matter – The Particulate Nature of Matter
Sprint Test
Check & Review Paper
Duration: 30 min (1 period)
(Optional for NA)
7 Model of Matter – The Particulate Nature of Matter
Sprint Test Answers