Topic 2 - Bonding, structure and properties of matter

Question 1

What structure do Ionic compounds have?

Answer 1

A regular lattice structure

Question 2

Describe the formation of ionic compounds?

Answer 2

1. They have a structure called a giant ionic lattice
2. The ions form a clsely packed regular lattice arrangement and there are very strong electromagnetic forces of attraction between oppositely charged ions, in all directions of the lattice

Question 3

What properties do ionic compounds have?

Answer 3

1. They all have high melting and boiling points due to the many strong bonds between the ions
2. It takes a lot of energy to overcome this attraction

Question 4

Can ionic compounds conduct electricity?

Answer 4

1. When they are solid the ions are held in place, so the compounds can’t conduct electricity
2. When ionic compounds melt, the ions are free to move and they’ll carry electric charge
3. Some ionic compounds also dissolve in water. The ions separate and are all free to move in the solution, so they’ll carry electric charge.

Question 5

What bonds do a metal and non metal form?

Answer 5

Ionic bonds

Question 6

What bonds do non-metals form?

Answer 6

Covalent bonds

Question 7

What bonds do metal atoms form?

Answer 7

Metallic bonds

Question 8

Describe covalent bonding?

Answer 8

1. When non-metal atoms bond together, they share pairs of electrons to make covalent bonds
2. The positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces, making covalent bonds very strong
3. Atoms only share electrons in their outer shells
4. Each single covalent bond provides one extra shared electron for each atom

Question 9

What are simple molecular substances?

Answer 9

Simple molecular substances are made up of molecules containing a few atoms joined by covalent bonds

Question 10

Common examples of simple molecular structures?

Answer 10

1. Hydrogen
2. Chlorine
3. Oxygen
4. Nitrogen
5. Methane

Question 11

What are properties of simple molecular structures?

Answer 11

1. The atoms within the molecules are held together by very strong covalent bonds, but the intermollecular forces between the molecules are very weak
2. To melt or boil a simple molecular compound you only need to break these feeble intermollecular forces, not break the covalent bonds
3. This means they have very low melting and boiling points because the molecules are easily separated
4. Most simple molecular structures are liquids or gases at room temperature
5. As molecules get bigger, the strength of the intermollecular forces increases, so more energy is needed to break them, and the melting and boiling points increase
6. Molecular compounds don’t conduct electricity as there are no fre electrons or ions

Question 12

What are polymers?

Answer 12

Long chains of repeating units

Question 13

Properties of polymers?

Answer 13

1. In a polymer, lots of small units are linked together to form a long molecule that has repeating seactions
2. All the atoms in a polymer are joined by strong covalent bonds
3. The intermolecular forces between polymer molecules are larger than between simple covalent molecules, so more energy is needed to break them
4. This means most polymers are solid at room temperature
5. The intermolecular forces are still weaker than ionic or covalent bonds, so they generally have lower boiling points than ionic or giant molecular compounds

Question 14

Describe giant covalent structures?

Answer 14

1. In giant covalent structures, all the atoms are bonded to each other by strong covalent bonds
2. They have very high melting and boiling points as lots of energy is needed to break the covalent bonds
3. They dont have charged particles so they dont conduct electricity

Question 15

Three examples of giant covalent structures?

Answer 15

1. Diamond
2. Graphite
3. Silicon dioxide

Question 16

What are allotropes?

Answer 16

1. Allotropes are different structural forms of the same element in the same physical state

Question 17

Describe diamond?

Answer 17

1. Diamond is very hard
2. Diamond is a giant covalent structure, made up of carbon atoms that each form four covalent bonds
3. These strong covalent bonds take a lot of energy to break and give diamond a very high melting point
4. It doesnt conduct electricty as there are no free ions or electrons

Question 18

Describe graphite?

Answer 18

1. In graphite, each carbon atom only forms three covalent bonds, creating sheets of carbon atoms arranged in hexagons
2. There arent any covalent bonds between the layers - they are only held together weakly, so they are free to move over each other. This makes graphite soft and slippery, so it can be used as a lubricant
3. Graphite has a high melting point - the covalent bonds in the layers need loads of energy to break
4. It can conduct electricity. This is because only 3 out of each carbons 4 outer electrons are used in bonds, so each carbon atom has one delocalised electron.