1. Chemistry
Metallic Bonding

2. Metallic Bonding Introducing metallic bonding Properties of metals
Contents
Metallic Bonding
Introducing metallic bonding
Properties of metals
Summary activities

3. Metals in the periodic table
Metal are found at the left and centre of the periodic table. H He Rn Xe Kr Ar Ne Ra Ac Rf Db Sg Bh Hs Mt Ds Rg ? Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Mg Al Si P S Cl Be B C N O F Cs Rb K Na Li Fr

4. Metallic bonding
Atoms of metals or alloy are tightly packed together in a giant metallic lattice similar to the lattice in ionic compounds.
Sea of free electrons
metal atoms
metal ions
The outer electrons separate from their atoms and become delocalized, creating a ‘sea of electrons’. The atoms become positive ions and are attracted to these electrons.
This attraction is called metallic bonding and is the reason why the positive metal ions do not repel each other.

5. Electrons and metallic bonding
How is the sea of electrons involved in metallic bonding?

6. Metallic Bonding Introducing metallic bonding Properties of metals
Contents
Metallic Bonding
Introducing metallic bonding
Properties of metals
Summary activities

7. Properties of metals: density
Metal ions form a lattice which is more tightly packed and denser than the lattices in ionic compounds. They form crystals called grains.
Metals generally have a very high melting and boiling point because metallic bonds are very strong and so a large amount of energy is needed to break them.
Which metal has the lowest melting point?
Mercury has the lowest melting point of all metals, -39°C, and is liquid at room temperature.
Sodium melts at 98°C.

8. Properties of metals: conductivity
Metals are good conductors of:
heat – the free electrons can take in heat energy, which makes them move faster. They can then transfer the energy throughout the lattice.
electricity – the free electrons can carry an electrical charge.
Silver is the best conductor of electricity and copper is the second best.
Why is copper used instead of silver for electrical wires?

9. Properties of metals: strength
Metals are usually tough, not brittle. When a metal is hit, the layers of the lattice just slide over each other. The metallic bonds do not break because the electrons are free to move.
force
This means that metals are:
malleable – they can be bent and pressed into shape;
ductile – they can be drawn out into wires.

10. Metal grains
Layers of atoms can slip over each other in metal grains when a force is applied, but this slippage stops at grain boundaries.
grain boundary: where one grain meets another
The smaller the grains, the shorter the distance the atom layers can move. This means that metals with smaller grains are stronger and harder than metals with larger grains.
The faster that molten metal is cooled, the smaller the grain size.

11. Properties of metallic substances
Boardworks AS Chemistry
Structure and Shape
Properties of metallic substances
Teacher notes
The ‘conductivity’ animation shows the metal in its solid state, with the metal ions in fixed positions and the electrons free to move. It could be pointed out that when the metal is molten, the ions would also be free to move.

12. Metals and metallic bonding

13. Properties of metallic and ionic crystals
Boardworks AS Chemistry
Structure and Shape
Properties of metallic and ionic crystals

14. Predicting bonding

15. Properties of metallic and ionic crystals
Boardworks AS Chemistry
Structure and Shape
Properties of metallic and ionic crystals

16. Strengthening metals
Metals can be made stronger by adding another element when the metal is molten. The atoms of the new element spread through the crystal structure.
force
force
Because the atoms of the added element are larger, they make it difficult for layers of metal atoms to slide. This makes the metal less malleable and less ductile.
This process is called alloying, and the new substance is called an alloy.

17. Boardworks GCSE Science: Chemistry Metals and Alloys
What is an alloy?
An alloy is a mixture of a metal with at least one other element.
Steel is a common example of an alloy. It contains iron mixed with carbon and other elements.
Adding other elements to a metal changes its structure and so changes its properties.
The final alloy may have very different properties to the original metal.
Photo credit: © 2006 Jupiterimages Corporation.

18. What types of alloys are there?
Boardworks GCSE Science: Chemistry
Metals and Alloys
What types of alloys are there?
Alloys have been used for thousands of years. Bronze, an alloy of copper 90% and tin 10%, was commonly used by civilizations before iron extraction methods were developed (harder than copper).
Other well-known alloys include:
brass: an alloy of copper 70% and zinc 30%.
It does not tarnish and is used for door knobs, buttons and musical instruments –(gold coloured and harder than Cu)
solder: an alloy of ten 50% and lead 50%. It is used in electronics to attach components to circuit boards (mp lower than both metals ).
amalgam: an alloy of mercury and silver or tin. It is used for dental fillings because it can be shaped when warm
and resists corrosion.

19. Boardworks GCSE Science: Chemistry Metals and Alloys
What is steel?
Steel is stronger than pure iron and can be used for everything from sauce pans…
…to suspension bridges!

20. What types of steel are there?
Boardworks GCSE Science: Chemistry
Metals and Alloys
What types of steel are there?
Steel can contain up to 2% carbon.
Varying the amount of carbon gives steel different properties. For example, a higher carbon content makes a hard steel.
Different types of steel are classified
by how much carbon they contain.
high carbon steel contains more than 0.5% carbon.
low carbon steel contains less than 0.25% carbon.
mild steel contains iron 99.7% and 0.3% carbon.
Two other important types of steel are:
stainless steel – an alloy of iron 74% that contains at least
18% chromium and nickel 8% hard and does not rust.
titanium steel – an alloy of iron and titanium.

21. When is a copper coin not a copper coin?
Boardworks GCSE Science: Chemistry
Metals and Alloys
When is a copper coin not a copper coin?
When it is a copper-coated alloy!
Copper coins used to be made from pure copper but most ‘copper’ coins used around the world are now made from copper alloys or cupro-nickel alloy..
zinc, magnesium and 4 % copper are added to aluminium to create an alloy ( duralumin)that is light but very strong. This is used in building aircraft
Photo credit: © 2006 Jupiterimages Corporation.
Canadian copper coins.

22. Boardworks GCSE Science: Chemistry Metals and Alloys
Is gold an alloy?
Although pure gold is sometimes used in electronics, gold jewellery is always a mixture of gold and other metals.
Pure gold is actually quite soft. Adding small amounts of
other metals makes the gold hard enough to use in jewellery. Alloying gold with different metals also affects its colour.
The familiar yellow gold is an alloy of gold with copper and silver.
Photo credit (top and bottom): © 2006 Jupiterimages Corporation
Teacher notes
More information about gold is available at:
White gold is an alloy of gold with nickel, platinum or palladium.

23. Why is steel stronger than iron?
Boardworks GCSE Science: Chemistry
Metals and Alloys
Why is steel stronger than iron?
The atoms in pure iron are arranged in densely-packed layers. These layers can slide over each other. This makes pure iron a very soft material.
The atoms of other elements are different sizes. When other elements are added to iron, their atoms distort the regular structure of the iron atoms.
It is more difficult for the layers of iron atoms in steel to slide over each other and so this alloy is stronger than pure iron.

24. Using different types of steel
Boardworks GCSE Science: Chemistry
Metals and Alloys
Using different types of steel
Photo credits
low carbon steel structure (small image only): © 2006 Jupiterimages Corporation
swords (small and large image): © 2006 Jupiterimages Corporation
stainless steel forks (small and large image): © 2006 Jupiterimages Corporation
aeroplane/shuttle image (small and large image): NASA The space shuttle Discovery being transported from the NASA Dryden flight research centre to the Kennedy space centre, using a modified 747 aeroplane.
rotary blade (small and large image): © 2006 Jupiterimages Corporation
Teacher notes
This activity provides information about five important types of steel. The activity could be extended by asking students to suggest or research other types of steel.

25. Using different types of steel
Boardworks GCSE Science: Chemistry
Metals and Alloys
Using different types of steel
Teacher notes
This matching activity can be used as a plenary or revision exercise on the uses of steel. Students could be asked to complete the activity in their books or using mini-whiteboards and the activity could be concluded by the completion on the IWB.

26. Metallic Bonding Introducing metallic bonding Properties of metals
Contents
Metallic Bonding
Introducing metallic bonding
Properties of metals
Summary activities

27. Glossary
 alloy – A material containing two or more metals, or a metal and a non-metal.
 delocalized – Electrons that are free to move throughout a structure.
 ductile – Capable of being drawn out into a wire.
 grain – A crystal of metal.
 malleable – Capable of being bent and pressed into a different shape.
 metallic bonding – The strong attraction between positive metal ions and the ‘sea of electrons’.
 sea of electrons – Delocalized electrons from the outer shell of metal atoms and which move freely in metallic structures.

28. Anagrams

29. Multiple-choice quiz