KS3 Chemistry
8E Atoms and
Elements
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Contents
8E Atoms and Elements
What are atoms and elements?
Symbols for elements
Elements in the periodic table
Making compounds
Chemical reactions
Summary activities
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How many different substances are there?
How many
different substances
can you think of?
There are millions of different substances!
What are they all made of?
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All substances are made of atoms
All substances are made of very tiny particles called atoms.
Many substances are made up of different types of atoms.
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hydrogen and
oxygen atoms
carbon and
hydrogen atoms
iron, aluminium,
silicon, oxygen
and boron atoms
carbon, nitrogen,
hydrogen, oxygen
and sulphur atoms
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What is an element?
All substances are made of very tiny particles called atoms.
There are about one hundred substances that are made up
of just one type of atom. These are the elements.
carbon
helium
copper
The elements are the simplest substances in the universe.
The elements are the building blocks of all other substances.
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Atoms in elements
An element is a substance made up of only one type of atom.
Copper is an
element made up of
copper atoms only.
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Carbon is an
element made up of
carbon atoms only.
Helium is an
element made up of
helium atoms only.
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Atoms and molecules of elements
An element is a substance made up of only one type of atom.
In some elements, the atoms are joined in groups of two or
more. A particle containing atoms grouped in this way is
called a molecule.
Oxygen is an
element made up of
oxygen atoms only.
How many atoms
are there in an
oxygen molecule?
Other elements, that contain atoms joined in molecules are
hydrogen, nitrogen, chlorine and bromine.
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Contents
8E Atoms and Elements
What are atoms and elements?
Symbols for elements
Elements in the periodic table
Making compounds
Chemical reactions
Summary activities
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Introducing chemical symbols
A standard set of symbols is used to represent elements:
 The symbol for many of the more common elements uses
just the first letter of the name.
H = hydrogen
C = carbon
F = fluorine
 Others elements have
the first two letters.
Li = lithium
Al = aluminium
He = helium
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O = oxygen
N = nitrogen
I = iodine
 Some of the symbols are not
always as you might expect.
Pb = lead
Au = gold
Ag = silver
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Symbols as an international language
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How to write symbols for elements
Two important rules should be followed when writing the
symbols of elements so that there is no confusion.
1. The first letter of an element’s symbol is always
a capital letter.
e.g.
N (not n) for nitrogen
2. If there are two letters in the element’s symbol,
the second letter is always a small letter.
e.g.
Co (not CO) for cobalt
No, Watson! It was
carbon monoxide
poisoning – not cobalt.
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Chemical symbols game
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The Story of ‘The Kid’
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Spelling with symbols activity
Write down the symbols for each element listed and
use these to spell out a word that matches the clue.
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1. Board game: carbon, helium, two sulphurs
CHeSS
2. Relative: sulphur, oxygen, nitrogen
SON
3. Fuel: carbon, oxygen, aluminium
COAl
4. Group of fish: sulphur, hydrogen, oxygen,
aluminium
SHOAl
5. For the rubbish: boron, iodine, nitrogen
BIN
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Symbols for molecules of elements
In some elements, the atoms are joined together and
form molecules. Combining the symbols of the atoms
in a molecule gives you the formula of the molecule.
What is the formula for the molecules in each element?
oxygen
nitrogen
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O2
N2
There are
groups of
two atoms
in each
molecule.
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Contents
8E Atoms and Elements
What are atoms and elements?
Symbols for elements
Elements in the periodic table
Making compounds
Chemical reactions
Summary activities
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Arranging elements
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Metal or non-metal?
Is this element a metal or a non-metal ?
Hard to
say!
H
He
Li Be
B C N O F Ne
iron
(Fe)
antimony
(Sb)
iodine
(I)
copper
(Cu)
phosphorus
(P)
sulfur (S)(Mg)
magnesium
Na Mg
Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac Rf Db Sg Bh Hs Mt ? ? ?
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Metals and non-metals in the periodic table
The periodic table is a list of all the known elements which
are arranged according to the similarities in their properties.
Non-metals are
Metals are on the
mostly on the right.
left and in the centre.
Xe
What type of elements are between metals and non-metals?
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Types of elements in the periodic table
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Metal, non-metal or metalloid?
krypton
francium
(Kr)
(Fr)
silicon(Co)
(Si)
scandium
(Sc)
cobalt
H
Li Be
Na Mg
metalloid
non-metal
metal
Which
side
What are
areare
thethe
nonmetalloids?
metals on?
B C N O F
Al Si P S Cl
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I
Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At
He
Ne
Ar
Kr
Xe
Rn
Fr Ra Ac Rf Db Sg Bh Hs Mt ? ? ?
Metals are on
Metalloids sometimes
Non-metals
the left and in
behave like metals and
are mostly
the centre. sometimes like non-metals. on the right.
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Contents
8E Atoms and Elements
What are atoms and elements?
Symbols for elements
Elements in the periodic table
Making compounds
Chemical reactions
Summary activities
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Combining elements
How is possible to have so many different materials from
a limited number of elements?
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Combining elements
How do you get so many
different cheeses?
What is the key ingredient
in all cheeses?
Milk is combined with a
small number of ingredients
under different conditions to
make a huge number of
different cheeses.
In a similar way, a small number of elements can be
combined in many different ways to make a huge
number of different compounds.
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What is a compound?
A compound is the substance produced when two or more
elements combine in a chemical reaction.
Two elements, hydrogen (H)
and oxygen (O), combine to
make the compound, water.
Which two elements combine
to make the compound
carbon dioxide?
A compound is always made up of two or more
different types of atom.
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Making a compound – carbon dioxide
A compound has very different properties to the elements
from which it is made.
elements
carbon
oxygen
combines
with
A black solid
which can be
used as a fuel.
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compound
carbon dioxide
to make
A colourless gas
which is essential
for life.
A colourless gas
which is used
to put out fires.
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Making a compound – water
What are the elements which make up water?
In what ways are the elements different to their compound?
elements
oxygen
hydrogen
combines
with
A colourless gas
which is used in
hot air balloons.
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compound
water
to make
A colourless gas
which is essential
for life.
A liquid which is
essential to our
lives and has many
different uses.
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Element or compound?
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Element or compound?
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Contents
8E Atoms and Elements
What are atoms and elements?
Symbols for elements
Elements in the periodic table
Making compounds
Chemical reactions
Summary activities
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Chemical reaction to make water
In a chemical reaction new substances are formed.
Elements combine with each other to make new substances
called compounds.
+
hydrogen
oxygen
water
The substances which combine in a reaction are the reactants.
The new substances produced in a reaction are the products.
The products have different properties to the reactants from
which they are formed.
Compounds can also combine with elements or other
compounds to make new compounds.
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Atoms joining in a chemical reaction
When the two elements, hydrogen and oxygen, combine in a
chemical reaction, the hydrogen and oxygen atoms do not
just mix together they become joined to one another.
hydrogen
+
oxygen
water
H H
+ O
O
H H
In a chemical reaction, the atoms in the reactants
become joined in different ways and this is how
new substances are formed.
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Contents
8E Atoms and Elements
What are atoms and elements?
Symbols for elements
Elements in the periodic table
Making compounds
Chemical reactions
Summary activities
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Glossary
atom – The smallest particle that can exist on its own.
compound – Substance made up of two or more
different elements that are chemically joined together.
element – Substance made up of only one type of atom.
formula – The symbols and numbers that represent the
atoms in a substance.
molecule – Two or more atoms that are chemically joined
together.
periodic table – Table in which all known elements are
arranged based on their properties.
symbol – One or two letters that represent an element.
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Anagrams
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Multiple-choice quiz
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