Structure and Bonding

Question 1

Describe solids

Answer 1

Solids are extremely hard to compress because the particles are packed together in a regular pattern with almost no space between the particles.
Solids have a fixed shape and cannot flow from place to place. The particles vibrate about their fixed position.

Question 2

Describe liquids.

Answer 2

Also very difficult to compress as the particles are close together with not many spaces between them.
Liquids take the shape of their container and flow from place to place. The particles in a liquid can move.

Question 3

Describe gases.

Answer 3

Extremely easy to compress because the particles are widely spaced.
The gas particles spread out and fill the space of their container because the particles move quickly and randomly.

Question 4

How do you melt a solid?

Answer 4

Put in energy to break the forces of attraction between the particles in a solid.
Once they are broken, the particles can now move around. The stronger the forces, the more energy needed and the higher the melting point.

Question 5

What are the limitations of the simple particle model?

Answer 5

It assumes that all particles are solid spheres.

Assumes there are no forces between the particles.

Question 6

Describe the structure of ionic compounds

Answer 6

They form giant ionic lattices.
Every positive ion is surrounded by negative ions and vice versa.
These lattices are three-dimensional.
There are very strong electrostatic forces between the positive and negative ions.
These forces hold the positive and negative ions in place.
The ionic bonds (electrostatic forces) act in all directions.

Question 7

What are the properties of ionic compounds?

Answer 7

They have very high melting and boiling points.
This is because the strong electrostatic forces require a great deal of heat energy to break.
The particles vibrate when heated, and when they vibrate with enough energy, the forces break.

They cannot conduct electricity when they are solids.
This is because the ions cannot move: they are locked in place by the strong electrostatic forces of attraction.

Ionic compounds can conduct electricity when they are melted or dissolved in water.
The ions can now move and carry charge.

Question 8

What is a covalent bond?

Answer 8

A shared pair of electrons.

Question 8

What is a covalent bond?

Answer 8

A shared pair of electrons.

Question 9

Give examples of small covalent molecules

Answer 9

Hydrogen
Chlorine
Hydrogen chloride
Oxygen
Nitrogen
Ammonia
Methane
Water

Question 10

What are the properties of small covalent molecules?

Answer 10

They have low melting and boiling points so they are usually liquids or gases at room temperature. However there are weak intermolecular forces, so it doesn’t require a lot of energy to turn the molecules from a liquid to a gas.

As we increase the size of the small covalent molecule, the intermolecular forces increase. This means it requires more energy to break.

Small covalent molecules do not conduct electricity because they don’t have an overall electric charge.

Question 11

What are the general properties of giant covalent molecules?

Answer 11

Always solids at room temperature because they have millions of strong covalent bonds. So they have high melting and boiling points as they require lots of energy to break all of the bonds.

Question 12

What are the properties of diamond?

Answer 12

High melting and boiling point:
Each carbon atom forms four covalent bonds with other carbon atoms which means diamond has a huge number of covalent
bonds which require lots of energy to break.

Cannot conduct electricity:
There are no free electrons to carry electrical charge.

Question 13

What are the properties of silicon dioxide?

Answer 13

High melting and boiling point:

This is due to the huge the number of strong covalent bonds that require lots of energy to break.

Question 14

What are the properties of graphite?

Answer 14

High melting and boiling point:
Each carbon atom forms three covalent bonds. These atoms form hexagonal rings.
This means there are many covalent bonds so lots of energy is required to break them.

Soft and slippery:
The hexagonal rings are in layers. There are no covalent bonds between the layers so they can slide.

Excellent conductor or electricity and heat:
Each carbon atom has a single electron in the outer energy level which is not covalently bonded. These are delocalised electrons which can move.

Question 14

What are the properties of graphite?

Answer 14

High melting and boiling point:
Each carbon atom forms three covalent bonds. These atoms form hexagonal rings.
This means there are many covalent bonds so lots of energy is required to break them.

Soft and slippery:
The hexagonal rings are in layers. There are no covalent bonds between the layers so they can slide.

Excellent conductor or electricity and heat:
Each carbon atom has a single electron in the outer energy level which is not covalently bonded. These are delocalised electrons which can move.

Question 15

Compare graphite to metals

Answer 15

Not a metal as it is made up of carbon atoms.
Both good conductors of heat and electricity.
They both have delocalised electrons which can move.

Question 16

What are the properties of graphene?

Answer 16

Single layer of graphite so it is only one atom thick.

Excellent conductor of heat and electricity:
Delocalised electrons so it will be useful in electronics.

Extremely strong.

Question 17

What are fullerenes?

Answer 17

Molecules of carbon atoms with hollow shapes.

Usually have hexagonal rings of carbon rings.

Question 18

What is the first fullerene to be discovered?

Answer 18

Buckminsterfullerene.

Contains 60 carbon atoms arranged in a hollow sphere. They form 6 or 5 carbon atom rings.

Question 19

What are the uses of fullerenes?

Answer 19

Pharmaceutical delivery
Lubricants
Catalysts.

Question 20

What are carbon nanotubes?

Answer 20

Fullerenes shaped into long cylinders.
They have very high tensile strength so they can be stretched without breaking.
They are excellent conductors of heat and electricity.
They are also used to reinforce materials e.g. high end tennis rackets

Question 21

What are polymers?

Answer 21

Made by joining together thousands of small, identical monomers.
Monomers are often alkene molecules.

Question 22

Why are most polymers solids at room temperature?

Answer 22

The intermolecular forces of attraction between polymer molecules are relatively strong so it takes a lot of energy to break them.

Question 22

Why are most polymers solids at room temperature?

Answer 22

The intermolecular forces of attraction between polymer molecules are relatively strong so it takes a lot of energy to break them.

Question 23

Describe bonding in metals

Answer 23

Strong electrostatic attraction between the sea of delocalised negative electrons and the positive metal ions. The attractions are called metallic bonds.

Question 24

Properties of metals:

Answer 24

High melting and boiling points:
Requires a lot of energy to break the strong metallic bonds.

Excellent conductors of heat and electricity:
Delocalised electrons can move and carry an an electric current. They can also carry thermal energy.

Malleable:
The layers of atoms are able to slide over each other.

Question 25

What is an alloy and how do they work?

Answer 25

Mixture of metals.
The different sizes of atoms distorts the layers, making it more difficult for them to slide over each other.
Alloys are harder than pure metals.

Question 25

What is an alloy and how do they work?

Answer 25

Mixture of metals.
The different sizes of atoms distorts the layers, making it more difficult for them to slide over each other.
Alloys are harder than pure metals.