1. Covalent network lattices and covalent layer lattice

2. 3 Different types of Carbon
Charcoal, diamond and graphite are different physical forms of carbon ,
these are called allotropes of carbon.

3. Covalent Network Lattice
The carbon in Diamond is bonded very strongly in a 3D lattice making it hard and crystalline with a very high melting point.

4. Other examples of covalent network lattices
Silicon dioxide also called silica is found in quartz

5. Covalent lattices
Graphite is hard in two dimensions but slippery in another. The carbon in graphite is bonded in 2D layers.
Weak intermolecular bonds

6. Revision How are carbon dioxide molecules bonded together?
With Dispersion forces
Are Dispersion forces weak or strong?
Weak

7. Properties of covalent molecular, network and layer lattices
You can use the covalent molecular, network and lattice models to explain properties of non- metal compounds.

8. Melting and boiling points
When a substance melts the particles break out of their position (the intermolecular forces have been overcome).
For small molecules, the intermolecular forces are weak and therefore its does not take a lot of energy to overcome these forces, making melting and boiling points low
Network and layer lattices have high m.p. and b.p. because they covalent bonding throughout the lattices are very strong

9. c

10. Electrical conductivity
In Covalent molecular substances and covalent network lattices the electrons are localised and therefore cannot move
Graphite has one electron from each carbon delocalised and therefore these are able to carry and electric current

11. Chemical reactivity
Chemical reactivity is how well a substance reacts with other substances
Covalent network lattices and covalent layer lattices are very unreactive because they have such strong bonds
Small molecular substances are more reactive because their bonds are not as strong.

12. Hardness and softness
Covalent network lattices are very hard because they have strong covalent bonds and atoms are held in fixed positions
In covalent layer lattices the forces between layers are weak and layers can slide over one another
The intermolecular forces in Covalent molecular substances determines whether they will be hard or not
Because intermolecular forces are quite weak covalent molecular substances tend to be gases and liquids

13. Melting point (C) Fluorine (F2) -220 Chlorine (Cl2) -101 Bromine (Br2)
Explain the trend in the following melting points.
The trend is the increase in melting points of halogens down a group.
There is an increase in the melting points because the strength of intermolecular forces increases as you go down the halogen group. Iodine is heavier and has more electrons and therefore the London forces between iodine molecules are stronger than those between the smaller fluorine molecule. Stronger intermolecular forces result in a higher melting point
Melting point (C)
Fluorine (F2)
-220
Chlorine (Cl2)
-101
Bromine (Br2) -7
Iodine (I2)
114

14. The mass of the HF molecule is similar to the mass of a neon atom, yet there boiling points is very different. HF’s b.p. is 19.5C and Ne’s b.p is -246C. Explain this difference.

15. At room temperature , CCl4 is a liquid whereas CH4 is a gas
At room temperature , CCl4 is a liquid whereas CH4 is a gas. Why is this the case?
Both are tetrahedral, non polar covalent molecules so London forces occur between the molecules. The London forces between CCl4 are stronger than CH4. This is due to CCl4 being a larger or heavier molecule making the london forces stronger making it a liquid at room temperature.

16. As a group create a concept map using the following words
Polar Bond Non-polar bond Dispersion Forces Ionic Bonding Covalent Bonding Metallic Bonding Intermolecular Forces Intramolecular Forces Polar Molecule Non-polar Molecule Partial Positive Partial Negative Dipole Dipole Forces Covalent network lattice Hydrogen Bonding Covalent layer lattices

17. How is hydrogen bonding different from a dipole dipole interaction?
Pg 127 Question 13 and 15