Structure and bonding in metals

• In a metal the atoms are like tiny spheres, arranged in a regular structure• they are packed as close together as possible in each crystal, forming a giant structure.• The atoms are held together by metallic bonds, which are strong but flexible.• This is a good model because it explains all the data we have about metals

1) Structure of metalsTherefore, metals are STRONG and have HIGH MELTING POINT

• Metal atoms lose the electrons in their outer shell easily ,so become positive ions.

• Each metal atom contributes one or two electrons to a shared ‘sea’ of electrons.

• Overall the metal is not charged because the total negative charge of the electrons balances the total charge on the positive metal ions.

• The shared bonding electrons can move through the whole metal structure.

• This is why metals can conduct electricity - because the electrons can move freely between the ions.

2) Properties of metalsMetals have certain properties that mean they can be used for different jobs. You need to be able to link their properties to how they are used for the exam:-

1) Strength – this means metals are used for structures that need to be able to withstand high forces. Titanium is a good example; used in the hulls of submarines as it is strong enough to withstand the high pressure under a 6km depth of water without caving in. Titanium is also used for hip joints and racing cars

2) Malleability - this means metals can be bent or pressed into shape. They bend without breaking. A good example is aluminium which can be moulded under pressure to make cans

3) High melting points – this means metals can be used to make equipment that has to withstand high temperatures without melting, e.g. sterilising equipment, ovens etc

4) Electrical conductivity – metals can be used as wiring, e.g. copper and aluminium are good examples of metals which conduct electricity

To remember these four - SOME MONKEYS HIT ELEPHANTS

Metals

Malleable

Good conductors of electricity

Strong

High melting points

Questions:

1. Give 5 examples of metals used for their strength and give an example of their use

2. Which of these ideas about the arrangement of atoms on a copper crystal are true and which are false?

a) Copper crystals are shaped like cubes because the atoms are packed in a cubic pattern

b) There is air between the atoms in a crystal of copperc) Copper is dense because the atoms are closely packedd) The atoms in a copper crystal are not moving at room temperaturee) Copper has a high melting point because the atoms are strongly

bonded in a giant structuref) Copper melts when strongly heated because the atoms melt

3. There are positive metal ions in a metal crystal but a metal is not an ionic compound. Explain why

IMPACTS ON THE ENVIRONMENT DUE TO MINING, USE AND DISPOSAL OF METALS

Mining and electrolysis produces many valuable metals. However, there is a conflict between profit-making industries and protecting the environment.

Mining•Produces large volumes of waste rock•Leaves large holes in the ground•Explosives used to blast the rock – this produces noise and dust

Processing ores•Many metals have high value but low grade –this means you have to dig up a lot of rock to only get a small amount of useful metal out of it•For example, with copper mining, 99.6% of the rock dug up is waste. Only 0.4% is copper. This means waste tips are created for the 99.6% waste rock, which can also contain toxic metals like lead or mercury

Metals we use•Careful choice of which metals we use can reduce the environmental impact we cause•E.g. making lighter cars etc means lower fuel consumption and emissions•We can make vehicles lighter by replacing steel with lighter metals such as aluminium and plastics

IMPACTS ON THE ENVIRONMENT DUE TO MINING, USE AND DISPOSAL OF METALS

Recycling•Scrap metal from all stages of production and from the end of the life of a metal product is routinely recycled•Recycling means less mining and electrolysis, which is expensive, so it saves money

Impacts on the environment

PROCESSING ORES

RECYCLING

METALS WE USE

MINING

Questions:

1. Why are recycling rates for metal waste from manufacturing higher than recycling of metals after their use?

2. “Steel and aluminium products play a role in everything we do in modern-day life. So, although production of steel and aluminium consumes resources and energy, both materials make a major contribution to our quality of life.” Draw up a table to list the benefits and costs of our use of these two materials. Do agree with the claim made in this statement?