Transcript No Slide Title

•Periodic Table
•Metallic Bonding
•Uses
Metallic
of Metal
Bonding
•Extraction of
metal
•Conservation
Increasing Non-metallic Character
Decreasing Non-metallic Character
Melting
point and
boiling
point
decrease
down the
group.
Reactivity
of Group I
elements
increases
down the
group.
Atoms of alkali metal.
Form ions carrying one
positive charge (for
example, Li+, Na+, K+).
All react with non-metals to form
compounds. These compounds
are all white, crystalline and
soluble in water.
Reactivity of
Group II elements
increases down
the group.
Melting point and
boiling point
decreases down the
group similar to the
properties of Group I.
All react with nonmetals to form salts.
Atoms of alkaline
metals form ions
carrying two positive
charges (for
example, Be2+, Mg2+,
and Ca2+ ).
Metal atoms are
joined to each other in a
giant metallic structure
by metallic bond.
Metallic bond is a type of
bonding between the
negatively charged
electrons and positively
charged metal ions.
e-
e-
e-
e-
e-
e- e
e-
ee-
ee-
Metals generally have high
densities due to close packing
of their atoms.
metal
Metals have high
melting and boiling
point due to the giant
ionic lattice and strong
metallic bond.
Metals are good
conductors of electricity
due to the movement of
mobile electrons in a metal.
Metal part
of a screw
Light bulb
Do not touch a red hot
metal rod with bare hand
because metal is a good
conductor of heat.
Gate
Bridge
Most metals have high strength. They can
support a heavy load without breaking.
Force
exerted
Metal can be hammered into
thin sheet without breaking
Metals are malleable and ductile since the
non-directional metallic bond still hold the metal
atoms together.
When choosing a metal for a particular use, we need to
consider the following questions:
Does the metal need to be …….
Strong?
Light?
Shiny?
Cheap?
Resist
corrosion?
Metal with the best
corrosion resistance
Au
The metal which is the
best conductor of heat is
Copper
Cu
The most abundant metal found in the Earth’s crust
Al
With the lowest
density of all is
Metal with the highest tensile
strength is
The best electrical
conductor is …
and
as well.
Cu
Metal withthe lowest melting
point is
Sn
•Jewellery and decorations are
made of gold or silver due to
their attractive appearances.
•Pipe and sheet for roofing can
be made of lead.
•Copper for making
electrical wire in the house.
•Gate at the front door is
made of iron.
•Light bulb filament is made of
tungsten.
•Food cans are plated with tin.
•The body of a ship is protected
by attaching magnesium or
zinc blocks to it.
Silver bromide is used
in film developing
•Potassium and calcium
are used in manufacturing
fertilizers.
Uses of Aluminium
Use
Making aeroplanes
Reasons for use
 Light but strong
 Resists corrosion
Making cooking foil
 Very malleable
 Non-poisonous
 Resists corrosion
 Very good conductor of heat
Making window frames  Strong
 Resists corrosion
Uses of Copper
Use
Reasons for use
Making electrical  Very good conductor of electricity
wires
 Very ductile
 Resists corrosion
Making cooking  Very good conductor of heat
utensils
 Very malleable
 Strong
 Resists corrosion
 Non-poisonous
Uses of Gold
Use
Reasons for use
Making jewellery and coins  Attractive golden colour
 Resists corrosion
 Most malleable and ductile
Uses of Iron
Use
Making bridges, ships
and gratings
Reasons for use
 Strong
 Malleable
 Ductile
 Cheap
Uses of Lead
Use
Reasons for use
Pipes, sheets for roofing  Resists corrosion
 Easy to shape
 Cheap
Uses of Silver
Use
Making jewellery and
coins
Making electrical and
electronic components
Reasons for use
 Attractive silvery colour
 Resists corrosion
 Malleable
 Ductile
 Best conductor of electricity
 Resists corrosion
 Malleable
 Ductile
Uses of Tin
Use
Reasons for use
Coating for other  Resists corrosion
metals
 Malleable
 Non-poisonous
 Offers a clean adherent surface
for paints
Uses of Titanium
Use
Making supersonic aircraft
and space vehicles
Reasons for use
 Light but very strong
 Very high melting point
 Resists corrosion
Uses of Tungsten
Use
Reasons for use
Making light bulb  Very high melting point
filaments
 Gets ‘white hot’ without melting
Uses of Zinc
Use
Coating for iron
Reasons for use
 Resists corrosion
 Very malleable
Decide which metal(s) is/are most suitable
for making
a) high speed drill head
b) window frame
c) saucepan.
Ans:
a) iron
b) aluminium
c) copper
-Only a few metals such as gold (Au) and platinum(Pt)
exist as free elements in the Earth.
Gold
•Other metals occur as compounds in the
Earth’s crust. For example: Iron, Zinc,
Aluminium, Copper, Tin, Lead and Silver.
•Rocks that contain metal-containing compounds
are called mineral ores.. Metals are extracted
from these mineral ores.
Ag
Fe
Hg
Pb
Metal Extraction
•Metal can be extracted from the ores by
(i) __________
the ore alone,
heating
(ii) __________
with carbon and
heating
electricity .
(iii) by using ____________
Metal
Main metallic compound in the ore
Method of extraction
Sodium
(Na)
Magnesium
(Mg)
Aluminium
(Al)
Sodium chloride
(NaCl)
Magnesium carbonate
(MgCO3 )
Aluminum oxide
Al2 O3 2H2O
Electrolysis of
molten ore
Zinc
(Zn)
Iron
(Fe)
Lead
(Pb)
Copper
(Cu)
Mercury
(Hg)
Silver
(Ag)
Gold
(Au)
Zinc sulphide
(ZnS)
Iron(III) oxide
(Fe2O3)
Lead(II) sulphide
(PbS)
Copper iron sulphide
(CuFeS2)
Mercury(II) sulphide
(HgS)
Silver sulphide (Ag2S) or free
element of silver
Free element of Gold
(Au)
.
Sulphide heat in air Oxide
Oxide heat with carbon metal
Oxide heat with carbon metal
Similar to that of Zn
Sulphide controled heat in air
metal
Sulphide heat in air metal
Displacement from solution
or mechanical separation
Mechanical separation (to separate the metal from impurities
Use of Recycling Bag
Supply of metals in the Earth’s crust is limited, while the demand for
metals is kept increasing. Recycling is an effective way of conserving
metals as the cost is reduced and energy is saved. It also minimize the
environmental problems arose in metal extraction and waste disposal.
Old metal articles can be used again, it is a
waste to throw it away.
New materials have
already been used to
replace some metals.
For instance, copper
pipes can be replaced
by plastics ---- PVC and
telephone wires made
of optical fibres are
commonly used.
Importance of Recycling
- save metal resources
- save energy
- save other resources such as
water
- Environmental problems,
such as waste disposal and
mining problems, can be
reduced
Mining process
Problems in Recycling
-the cost of collecting the
scrap metals
- the cost of transporting
scrap metals to the recycling
plant
- the cost of melting and
purifying metal
- the cost of disposing the
waste from the recycling
process
1) Metal resources are limited, what should people do in
order to make the resources last longer?
Ans:
By conservation of metal resources:
recycling, reusing and replacing metals
with other materials.
silver
16 years
tin
17 years
lead
.copper
iron
aluminium
26 years
36 years
2) Refer to Fig. 9.3 on your
textbook, why will the
resource of Al last longer
than other metals?
190 years
250 years
An estimate of how long the resources of some metals will last
Ans:
It is because Al is the most abundant
metal on the earth crust.
.
3) Which of the following Al articles is easier to recycle - Al
drink can or an aircraft made of Al alloy (a mixture of
metals)? Explain your answer.
Ans:
Drink can is easier to recycle
because it only contains a metal,
while the aircraft is made up of
more than 1 metal, this require
separation of metals before
recycling process can take place.