Bonding structure and the properties of matter

Question 1

What are ionic substances?

Answer 1

They are made of ions which are electrically charged particles. therefore they will have a different number of protons and electrons.

Question 2

What type of compounds have an ionic structure?

give 2 examples

Answer 2

most compounds made from a combination of metals and non metals have an ionic structure
eg sodium chloride NA= metal CL = non metal
copper sulphate Cu = metal S and O2 = non metal

Question 3

Describe the structure of an ionic substance

Answer 3

it is a giant lattice of positive and negative ions. iIt contains a massive number of particles in a regular pattern.

Question 4

What is ionic bonding?

Answer 4

it is the electrostatic attraction between positive and negative ions . Each ion is attracted to the ions around it which have an opposite charge.

Question 5

Properties of ionic substances

Answer 5

1. They have very high melting and boiling points because the attraction between the ions needs so much energy to break
2. They are solids at room temperature because the attraction is so strong.
3. The do not conduct electricity, because electricity is the flow of electrically charged particles and the bonds are too strong so the ions cannot move.
4. If they are dissolved in water the ions separate and they can then conduct electricity.

Question 6

How to work out the formula of ionic substances

Answer 6

Look at the periodic table
Group 1 have one electron in their outer shell so K+ Na +
Group 2 have 2 electrons in their outer shell so Ca++, Mg ++
Group 6 have 6 electrons in their outer shell so need 2 O - - and S- -
Group 7 electrons in their outer shell so need one more Cl- and Br-

Question 7

How do you work out the ratio of elements in a formula

Answer 7

It depends on the number of ions, so if they are the same the ratio will be 1:1 eg Na+Cl- or Mg++ O–
If they are different they need to balance
eg Cu++ Cl- so we need two Cl- to balance therefore the formula is CuCl 2

Question 8

Name some ionic substances which contain more than one element and give their charges

Answer 8

Sulphate SO4  --
Nitrate NO3 -
Carbonate CO3 --
Hydroxide OH -
Ammonium NH4 ++

Question 9

Name 3 ionic substances which change their name slightly and give their charges

Answer 9

Sulphide S-
Chloride Cl-
Oxide O2 –

Question 10

Explain how dot and cross diagrams work and give an example.

Answer 10

In an ionic compound one element is shown with dots (metals) representing its outer shell the other with crosses (non metals). The dots of the metal are combined with the crosses of the non metal

Question 11

What is a molecular substance

Answer 11

it is made from molecules which are atoms joined together by covalent bonds. Some non metals are made of molecules eg CL2, H2 and O2

Question 12

Name and give the formula of 5 common molecular compounds

Answer 12

water H20
ammonia NH3
glucose C6H12O6
nitrogen N2
sugar C11H22O11
methane CH4
ethanol C2H5OH

Question 13

Describe the structure of a molecular substance

Answer 13

It is made of many identical molecules but they are not joined to each other. Within each molecule the atoms are joined by very strong covalent bonds but the forces between the molecules are weak and are called intermolecular forces.
Some molecules are small containing only a few atoms such as water. Others are huge like nylon and polythene.

Question 14

Properties of molecular substance

Answer 14

1. They have low boiling and melting points.
2. Many are gases or liquids at room temp
3. They do not conduct electricity as they do not contain charged ions.

Question 15

Why do molecular substances have low boiling and melting points?

Answer 15

Because the molecules are not bonded and have only weak intermolecular forces the forces do not need a lot of energy (heat) to overcome.

Question 16

What is the difference between a molecular formula and an empirical formula for a molecular substance?

Answer 16

The molecular formula shows the number of atoms of each element in every molecule eg in glucose C6H12O6
The empirical formula only shows the ratio of the atoms so in glucose this would be CH2O. It is more common to use the molecular formula.

Question 17

What is a stick diagram for a molecule?

Answer 17

Stick diagrams show the number of bonds between each atom. They can be single sticks double sticks or even triple sticks. Unlike dot and cross diagrams they do not show the outer shell electrons.
eg O-H-O O=C=O

Question 18

What is the relationship between the number of covalent bonds and the electronic structure in molecular substance?

Answer 18

The number of covalent bonds is equal to the number of electrons needed to have a noble gas structure. So group 1 need to lose one electron therefore form 1 bond and group 7 need to gain 1 and also form one bond.
Groups 2 and 6 it is 2 bonds. Groups 3 and 5; 3 bonds and group 4; 4 bonds.

Question 19

What is a polymer? and give some examples of them.

Answer 19

It is a long chain molecule made by joining lots of smaller molecules ( monomers) together by covalent bonds
Eg polythene, PVC, perspex, polystyrene

Question 20

Polymers are often represented with a stick diagram of the monomer in brackets with an n outside the bracket.
What does the n stand for?

Answer 20

The n is the number of times the basic structure in brackets (monomer) is repeated

Question 21

Describe the structure of metals

Answer 21

Metals consist of

1. A giant lattice
2. If positively charged ions
3. arranged in a regular pattern
4. the outer shell electrons are delocalised which means they can move freely throughout the structure
5. there is a strong attraction between the positive nucleus and the delocalised electrons (metallic bonding)

Question 22

Describe and explain the properties of metals

Answer 22

1 D- they have high melting and boiling points because E- the metallic bonds in the structure are strong

2. D-They can conduct electricity because E- the delocalised electrons can move freely so can carry an electrical charge through the structure.
3. D- They are good thermal conductors because E heat energy is transferred by the delocalised electrons
4. D- They are malleable (can be bent or hammered in shape) because E- the layers of atoms can slide over each other without breaking the metallic bonds

Question 23

What are alloys?

Answer 23

An alloy is a mixture of a metal with another substance- often another metal. it makes the metal harder and more useful.

Question 24

Explain why alloys are used?

Answer 24

Having a mixture of metals make the metal harder and more useful because instead of all of the atoms being the same size some are bigger than others. Therefore it is more difficult for the layers of atoms to slide across each other. Therefore the alloy is less malleable.

Question 25

Give 2 examples of alloys and their uses.

Answer 25

1. Gold alloy in jewelry so that it will hold it’s shape.

2. Steel is an alloy of iron and used in construction as it is harder and will survive greater weight bearing.

Question 26

Name the three types of bonding in substances

Answer 26

1. Ionic
2. Covalent
3. Metallic

Question 27

What is covalent bonding? Give 2 examples.

Answer 27

Atoms which are joined together by sharing pairs of electrons.
Eg. Any molecular substances such as NaCl or polythene

Question 28

What is metallic bonding? Give 2 examples.

Answer 28

The attraction between the positive nucleus and the delocalised electrons of a metal
Eg. Any metal gold, iron etc

Question 29

Identify the 5 different types of structure which make up all substances.

Answer 29

1. Giant covalent
2. Ionic
3. Metallic
4. Molecular
5. Monatomic

Question 30

Describe the structure of a giant covalent substance and give 3 examples

Answer 30

It is made of a giant lattice of atoms joined together by covalent bonds.
Eg. Diamond, graphite, silicon, silicon dioxide

Question 31

Describe and explain the properties of giant covalent substances

Answer 31

1. D Very high melting and boiling points because E they have lots of strong covalent bonds which would take a lot of heat energy to break down
2. D Non conductors of electricity (except graphite) because they do not have delocalised electrons

Question 32

Describe the structure of monatomic substances and give 2 examples

Answer 32

They are made of separate atoms which are not bonded together, there are very weak bonds between them
Eg any group 0 element, argon neon etc

Question 33

Describe and explain the properties of monatomic substances

Answer 33

1. D- Very low melting and boiling points because E they only have very weak forces between the atoms and are not bonded. All exist as gases.
2. Non conductors as there are no delocalised electrons or ions

Question 34

Identify 5 of the different forms of carbon

Answer 34

1. Diamond
2. Graphite
3. Graphine
4. Fullerine
5. Carbon nanotubes.

Question 35

Explain the structure of diamond and it’s properties

Answer 35

Diamond has a giant covalent structure, each carbon atom is bonded to 4 others.
1. Very high melting and boiling points because they have lots of strong covalent bonds which would take a lot of heat energy to break down
2. It makes it very hard because the atoms are held in a rigid network
3. It can’t conduct electricity because it has no delocalised electrons
It is used for the tips of drills because it is so hard, it can cut glass and stone.

Question 36

Explain the structure of graphite and it’s properties

Answer 36

Graphite has a giant covalent structure, the carbon atoms are bonded in flat layers but the layers are not bonded to each other. so each carbon atom is bonded to only 3 others, this leaves one electron in it’s outer shell free and delocalised.
1. Very high melting and boiling points because they have lots of strong covalent bonds which would take a lot of heat energy to break down.
2. It is soft because the layers of atoms can slide across each other
3. It can conduct electricity because it has delocalised electrons
Used in pencils and electrodes

Question 37

Explain the structure of graphine and it’s properties

Answer 37

A newly discovered substance which is a single layer of graphite, so it has a giant covalent structure and because each atom is only bonded to 3 others it has delocalised electrons.
1. Very high melting and boiling points because they have lots of strong covalent bonds which would take a lot of heat energy to break down.
2. Very strong due it’s strong covalent bonds.
3. Semi see through because it is so thin, only one layer thick
4. Thermal and electrical conductor because it has delocalised electrons.
It’s uses are only just being discovered because it is so new but it can be used in touch screens and other electronics.

Question 38

Explain the structure of fullerine and identify 3 of its uses.

Answer 38

The molecule C60 was the first to be identified and is shaped like a football. The rest of the family all have carbon atoms in hexagonal rings with a hollow part in the centre.
1 Used for delivering drugs into specific cells in the hollow centre
2 Used in lubricants to reduce friction as the spherical shape allows the molecules to roll over each other
3 As catalysts

Question 39

Explain the structure of carbon nanotubes and their properties.

Answer 39

Cylindrical tubes of carbon atoms arranged in a hexagonal structure, like tubes of graphine sheets.
1. They have high tensile strength due to having lots of strong covalent bonds
2. Good thermal and electrical conductor because it has delocalised electrons.
Used to strengthen items such as tennis rackets and golf clubs.

Question 40

What is the formula and electronic charge of sulphate?

Answer 40

SO4 2 minus