1. Bonding, Structure and Chemical Properties
CHEMISTRY 2
GCSE Additional Science
Chapter 7

2. The Periodic Table GCSE Additional Science Chapter 7 Non Metals Metals1 He 2 Li 3 Be 4 B 5 C 6 N 7 O 8 F 9 Ne 10 Na 11 Mg 12 Al 13 P 15 S 16 Cl 17 Ar 18 K 19 Ca 20 Sc 21 Ti 22 V 23 Cr 24 Mn 25 Fe 26 Co 27 Ni 28 Cu 29 Zn 30 Ga 31 Ge 32 As 33 Se 34 Br 35 Kr 36 Rb 37 Sr 38 Y 39 Zr 40 Nb 41 Mo 42 Tc 43 Ru 44 Rh 45 Pd 46 Ag 47 Cd 48 In 49 Sn 50 Sb 51 Te 52 I 53 Xe 54 Cs 55 Ba 56 La 57 Hf 72 Ta 73 W 74 Re 75 Os 76 Ir 77 Pt 78 Au 79 Hg 80 Tl 81 Pb 82 Bi 83 Po 84 At 85 Rn 86
GCSE Additional Science
Chapter 7
Metals

3. Comparing the properties of metals and non-metals
Good conductors of electricity
Poor conductors of electricity
Good heat conductors
Poor heat conductors
Malleable (can be moulded into shape)
Non-malleable (brittle in their solid form)
Ductile (can be pulled into wires)
Non-ductile
Shiny (when freshly cut)
Not usually shiny
Many have high melting points
Low melting point
Many have high boiling points
Low boiling point
GCSE Additional Science
Chapter 7

4. Metals GCSE Additional Science Chapter 7
The key to understanding a metal’s properties lies in its structure
positive ions
A metal structure is an ordered pattern of positive ions in a ‘sea’ of negative electrons.
free electrons
Ductility
Electrons act as a type of lubricant between the layers of ions. This explains why it’s possible to pull metals to form wires.
Electrical Conductors
Connecting the sides to a battery makes the electrons move from the negative side towards the positive – this is the flow of current.
Explaining the
properties of
METALS
GCSE Additional Science
Chapter 7
Melting Point
The strength of metallic bonds depends on the number of outer electrons in the atoms (the more outer electrons there are , the higher the melting point).

5. Alloys Metallic Glass GCSE Additional Science Chapter 7
Stainless steel is an example of an alloy used to make saucepans and cutlery.
Some modern alloys can recover their shape after bending. These are used in frames for glasses. They are a type of ‘smart material’ called shape-memory alloy.
Metallic Glass
As mentioned previously, most solids have a structure that shows a regular pattern but it’s possible to form metals that show less of a pattern – these are the metallic glasses.
GCSE Additional Science
Chapter 7
Metallic glasses are three times as strong as steel and ten times more flexible, making them ideal for use as golf club-heads.

6. BONDING Ionic Structures
Sodium chloride is formed when atoms of sodium bond with atoms of chlorine.
Cl-
Na+
GCSE Additional Science
Chapter 7
Sodium atom (Na) [2.8.1]
Sodium ion (Na+) [2.8]
Chlorine atom (Cl) [2.8.7]
Chloride ion (Cl-) [2.8.8]
Both atoms are trying to achieve a full set of outer electrons. They can do this if the sodium atom gives its outer electron to the chlorine atom.
We now have a sodium ion Na+, and a chloride ion Cl-.

7. BONDING Ionic Structures
Na+
Chloride ion (Cl-) [2.8.8]
Sodium ion (Na+) [2.8.]
Cl-
GCSE Additional Science
Chapter 7
Sodium chloride (salt)

8. BONDING Ionic Structures
So there are two types of ion:-
Positive ion (cation) – the atom has lost an electron or electrons.
Negative ion (anion) – the atom has gained electron(s).
The ions attract and the attraction is ionic bonding.
BONDING Ionic Structures
The oppositely charged ions attract each other. They cluster around each other (six Cl- around each Na+ and vice versa) to make an ionic giant structure.
Six Chloride ions cluster around one Sodium ion
GCSE Additional Science
Chapter 7
Six Sodium ions cluster around one Chloride ion
Molecular structure of Sodium Chloride
(Click molecule to show animation)

9. Properties of Ionic Compounds
PROPERTY
DUE TO
High melting point
Strong electrostatic forces of attraction between the ions. A lot of energy is needed to break them.
Solid ionic compounds do not conduct electricity.
The ions are held in fixed positions, and are not free to move.
Molten ionic compounds conduct electricity.
Melting has separated the ions so that they can move past each other.
GCSE Additional Science
Chapter 7

10. BONDING Covalent Bonding
Non-metal atoms bond with each other by sharing outer shell electrons.
This is called COVALENT BONDING.
Covalent bonding can produce:
Small molecules of elements, e.g. H2
Small molecules of compounds, e.g. HCl
GCSE Additional Science
Giant molecules of elements, e.g. diamond and graphite
Chapter 7
Giant molecules of compounds, e.g. SiO2

11. BONDING Covalent molecules
Some elements form covalent compounds. This happens as atoms share electrons. H Cl
GCSE Additional Science
Chlorine atom (Cl) [2.8.7]
Hydrogen atom (H) [1]
Chapter 7
Molecule of hydrogen chloride (HCl)
Hydrogen has the electron pattern of helium, and chlorine has the electron pattern of argon.
This is written as H-Cl, where the ‘-’ represents a covalent bond (pair of shared electrons).

12. Properties of molecular covalent compounds
Melting points
Low
(attraction between molecules is weak)
Physical state at room temperature
Gases or liquids with low boiling points or solids with low melting points
(weak forces of attraction between molecules)
Electrical conductivity
Do not conduct electricity
(the molecules have no charge)
Solubility in water
Most are insoluble in water
GCSE Additional Science
Chapter 7

13. An exercise to recognise atomic or covalent bonds
An exercise to recognise atomic or covalent bonds. (Only the outer shell is shown in the diagrams) H
Ca2+ F- 2 H O
ionic
covalent Cl
covalent
Mg2+ Cl- 2
covalent
ionic O
GCSE Additional Science
Chapter 7 N H Cu
Cu O2-
covalent
ionic
Show the answers

14. Comparing the properties of graphite and diamond
Giant Covalent Structures
Comparing the properties of graphite and diamond
Some covalent molecules exist as giant covalent structures. These have a high melting point because all the atoms are held by strong covalent bonds. Graphite and diamond are examples of giant covalent structures made up of a collection of carbon atoms only.
PROPERTY
Appearance
Transparent crystals
Grey/ black shiny solid
Hardness
Incredibly hard – used for cutting glass and in drill bits for drilling through rocks in the oil industry.
Very soft – used as a lubricant. Also used to make pencils.
Conductivity
Electrical insulator
A non-metal that conducts electricity. Used for making electrodes.
Melting point
Very high – over 3500°C.
Very high – over 3600°C.
Diamond
Graphite
GCSE Additional Science
Chapter 7

15. An explanation of the properties of diamond and graphite
Graphite has layers formed from hexagonal rings – these layers can slide over each other, and this is why it is used as a lubricant.
Every atom is bonded to 4 other atoms. Every outer electron has its role to play in the covalent bonding that happens here. The result is a very rigid structure. As there are no free electrons, it doesn’t conduct electricity and it’s a good conductor of heat.
GCSE Additional Science
Chapter 7
Every carbon atom bonds strongly to other carbon atoms by three covalent bonds. The fourth outer electron in each atom is free to move, and this is what makes graphite a good conductor.

16. The future, and other forms of carbon
Whilst experimenting with Fullerene C60, it was found that other structures of carbon could be formed. One of them is seen below:
Fullerene C60
Carbon Nanotube
The carbon atoms are bonded covalently into a football shape.
The nanotube is like rolled graphite.
It conducts electricity
It’s very small – 10,000 times thinner than a human hair
Crystals can be grown inside it
They may solve the problem of how to produce smaller circuits, where they might replace wires.
GCSE Additional Science
Chapter 7
Nanotube
Human hair