Transcript Lecture Notes Elements[1]

ELEMENTS
The Simplest Matter
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Elements
Definition of Elements:
An element is a substance which cannot be split into
two or more simpler substances by chemical
reactions.
Every element is given a name and a chemical symbol.
For e.g. Sodium(Na), Magnesium(Mg), Carbon(C)
Oxygen gas (O2), etc
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Abundance of Elements
•
109 have been discovered so far
•
92 elements occur naturally while the rest are
man-made
•
Most elements are found combined with other
elements in the form of ores or minerals
•
Some elements such as gold, sulphur, oxygen,
nitrogen, neon, helium occur naturally in their
free or uncombined state
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For your interest …
Find out the following:
(a) What is the most abundant element in the
earth's crust?
(b) What is the most abundant metal in the
earth's crust
(c) What is the most abundant element in the
earth's atmosphere?
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Classification of Elements –
Periodic Table
• The elements have been classified according to
their chemical properties into a chart called the
Periodic Table as shown below.
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In the periodic table…
In the periodic table,
• Each vertical column is called a group.
Elements in a group have similar chemical
properties. Each group has its own unique
properties.
• Each horizontal row is called a period.
Elements in a period from left to right show
a gradual change from metallic properties to
non-metallic properties.
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In the periodic table…
In the periodic table,
• Each element is represented by chemical
symbol.
Chemical Name
Aluminium
Zinc
Copper
Magnesium
Mercury
Chemical Symbol
Al
Zn
Cu
Mg
Hg
Note: Shown on this slide are common elements
you need to know.
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In the periodic table…
Chemical Name
Iron
Note the
spelling of
Carbon
“sulfur”. No
Sulfur
longer
“sulphur”.
Chlorine
By extension,
Nitrogen
Sulfate,
Iodine
sulfide,
Sulfuric acid.
Hydrogen
Oxygen
Chemical Symbol
Fe
C
S
Cl
N
I
H
O
Note: Shown on this slide are common elements
you need to know.
Classification of Elements
Elements can be classified into :
• Metals
e.g. aluminium, calcium, copper, mercury,
iron, zinc
• Non-metals
e.g. oxygen, hydrogen, helium, iodine,
sulphur
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Physical Properties of Metallic &
Non-metallic Elements
Metallic element
Non-metallic
elements
High melting and
boiling points
Low melting and
boiling points
(exists as solids at
room temperature
except for mercury
which exists as a
liquid)
(exists as solids,
liquids or gases at
room temperature)
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Physical Properties of Metallic &
Non-metallic Elements
Metallic element
Non-metallic
elements
Good heat
conductors
Poor heat
conductors
Good electrical
conductors
Poor electrical
conductors
(except for graphite)
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Physical Properties of Metallic &
Non-metallic Elements
Metallic element
Ductile
(can be drawn into
wires)
Malleable
(can be beaten into
shapes without
breaking)
Non-metallic
elements
Non-ductile or
snap easily
(cannot be drawn
into wires)
Brittle
(easily broken when
beaten)
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Physical Properties of Metallic &
Non-metallic Elements
Metallic element
Shiny
Non-metallic
elements
High densities
Dull in
appearance (not
lustrous)
Low densities
Sonorous
Not sonorous
(lustrous)
(produce a ringing
sound when hit)
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Uses of some elements
Sulfur
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Uses of some non-metallic elements
Carbon exists in
several different
forms (called
allotropes) diamond, graphite,
soot, charcoal
Diamond is the hardest
natural substance.
Thousands of tiny
diamonds are attached
to saws and drills for
cutting concrete and
drilling into rocks.
Uses: pencil leads, fuel, constitutes
living tissues
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Uses of some non-metallic elements
This gas is an
unreactive
element. It does
not combine
readily with other
elements.
Hence it can be
used in the
packing of food
It is also used in
the making of
fertilisers.
Uses: fertilisers, freezing agent for
food, constitutes plants and
animal proteins
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Uses of some non-metallic elements
Sulfur is a yellow
non-metallic
element, found in the
free state.
It is used to harden
rubber used for
making tyres.
It is also used in the
manufacture of
sulfuric acid,
pesticides and drugs.
Uses: drugs, fireworks, to harden
rubber, insecticides,
medicinal drugs
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Uses of some non-metallic elements
Iodine is a nonmetallic element
that sublimes when
heated to form a
violet vapour.
When dissolved in
ethanol, it forms
tincture of iodine,
used as an
antiseptic.
Uses: antiseptic
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Uses of some non-metallic elements
Oxygen is the
most important
gaseous element
to all living
organisms on
earth
They need it for
respiration.
Uses: combustion, respiration
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Uses of some non-metallic elements
Name of non-metallic
element
Chlorine
Fluorine
Silicon
Uses
Bleaching powder, kills
bacteria, used in making
plastics (PVC)
Prevents tooth decay
Transistors, manufacture
of steel
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Uses of some metallic elements
Zinc is used to
coat iron sheets
to make
galvanised iron.
It is also mixed
with copper to
form the alloy,
brass.
Uses: roofs, dry cell casings
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Uses of some metallic elements
Mercury is the only
metallic element
that is a liquid at
room temperature.
It is used in liquidin-glass
thermometers,
fluorescent lamps
and some dental
fillings
Uses: fluorescent lamps,
thermometers
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Uses of some metallic elements
Magnesium
burns with a
white dazzling
light and so it is
used in distress
flares.
It is also used in
making
fireworks.
Uses: fireworks
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Uses of some metallic elements
Aluminium, being
strong, and of low
density is used to make
aeroplane parts.
This metal is also used to
make drink cans,
cooking utensils and
ladders.
Being a good electrical
conductor and of low
density, it is also used to
make overhead
electricity cables.
Uses: pots and pans, foil
wraps, window and
door frames, light alloy
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Uses of some metallic elements
This metal is commonly
used to make electrical
wires as it is a good
electrical conductor and
is inexpensive.
It is also used to make
water pipes.
When mixed with tin, it
forms the alloy called
bronze and when mixed
with zinc, it forms the
alloy called brass.
Uses: electrical wires and
switches, coins, water
pipes, tanks
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Uses of some metallic elements
Name of metallic element
Calcium
Iron
Lead
Uses
For the body to grow
strong teeth and bones
Manufacture of steel,
railings, grills, cooking
utensils
Lead shots, accumulators
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