covalent bonding etc

Question 1

define covalent bonding

Answer 1

Electrostatic attraction between protons in two nuclei and a shared pair of electrons between them

Question 2

similarity between simple molecular and giant covalent

Answer 2

covalent bonding

Question 3

describe diamond

Answer 3

Diamond is a form of pure carbon arranged into a giant lattice like this:
This is a representative part of the lattice.
* Every C makes 4 covalent bonds
* Tetrahedral shape
* Strong, grid-like arrangement
Diamond sublimes at a very high temperature because:
* Covalent bonds are very strong
* There are lots of bonds in the giant lattice
* Lots of energy is required to break all the bonds
It is one of the hardest substances for the same reasons, so it is used in cutting.
It cannot conduct electricity, because there are no freely-moving charged particles.
All the atoms are neutral, and all the electrons are stuck inside an atom or a bond.

Question 4

describe silicon dioxide

Answer 4

Silicon dioxide (SiO2) is also known as silica.
It has a giant covalent structure:
This is a representative part of the lattice.
* Every Si makes 4 covalent bonds (black)
* Every O makes 2 covalent bonds (red)
* Tetrahedral shape (like diamond)
* Strong, grid-like arrangement
Silicon dioxide has similar properties to diamond because of its similar bonding and structure.
But it’s much less expensive because it is much less rare

Question 5

describe graphite

Answer 5

Graphite is another form of pure carbon arranged into a different giant lattice:
This is a representative part of the lattice.
* Layers of hexagons of C atoms
* Every C makes 3 covalent bonds (red)
* Weak forces between layers (blue)
* Delocalised electrons inside each layer
Graphite sublimes at a very high temperature, for the same reasons as diamond (see above).
It is soft and slippery because the layers can slide easily, so it is used as a solid lubricant.
It also conducts electricity, because inside the layers the delocalised electrons can move freely.

Question 6

describe c60 fullerene

Answer 6

C60 fullerene is a unique simple molecule composed of sixty carbon atoms in a ball:
Its boiling point is low, but not as low as other molecules because of its high molecular mass:
Water Chlorine Ammonia C60 fullerene
Formula H2O Cl2 NH3 C60
Molecular Mass = 720
BP = +600
It’s a soft and slippery solid because the molecules can roll over each other easily.
It is an electrical insulator because the molecules are neutral

Question 7

explain boiling points in simple molecular substances

Answer 7

Although simple molecules contain very strong covalent bonds, there are also weak
intermolecular forces (IMFs) between the molecules.
When simple molecular substances boil, it’s the weak IMFs which break
As molecular mass increases, so does the strength of the weak IMFs.
This results in the boiling point increasing

Question 8

describe electrical conductivity in simple molecular substances

Answer 8

Electrical conductivity requires charged particles that can move freely.
But in a simple molecular substance, there aren’t any charged particles:
Simple molecular substances never conduct electricity because molecules are neutral

Question 9

what elements does covalent bonding occur between

Answer 9

non metals

Question 10

4 properties of simple molecular substances

Answer 10

Low MP/BP
Insulator
Usually insoluble in water
Dull