Topic 2: Bonding, Structure and the Properties of Matter

Question 1

What is ionic bonding?

Answer 1

Ionic bonding is the electrostatic attraction between positive and negative ions.

It is a relatively strong attraction.

Question 2

How are ionic compounds held together?

Answer 2

• They are held together in a giant lattice.
• It’s a regular structure that extends in all directions in a substance.
• Electrostatic attraction between positive and negative ions holds the structure together.

Question 3

State properties of ionic substances

Answer 3

• High melting and boiling points (strong electrostatic forces between oppositely charges ions)
• Do not conduct electricity when solid (ions in fixed positions).
• Conduct when molten or dissolved in water - ions are free to move.

Question 4

Give 5 examples of positive ions and 5 examples of negative ions.

Answer 4

E.g. Positive: Na^+, Mg^2+, Al^3+, Ca^2+, Rb^+

E.g. Negative: Cl^-, Br^-, SO4^2-, NO3^-, OH^- (chloride, bromide, sulfate, nitrate, hydroxide).

Question 5

What is important when working out a formula of an ionic compound?

Answer 5

Ionic compounds are electrically neutral, i.e positive and negative charges balance each other.

Question 6

How are ionic compounds formed? Explain in terms of MgO case.

Answer 6

Reaction of a metal with a non-metal.
Electron transfer occurs - metal gives away its outer shell electrons to non-metal.
Mg is in Group II, so had 2 available outer shell electrons.
O is in Group VI, so can accept 2 electrons to get a full outer shell configuration.

Question 7

What is a covalent bond?

Answer 7

Covalent bond is a shared pair of electrons between two atoms.

Question 8

Describe the structure and properties of simple molecular covalent substances

Answer 8

• Do not conduct electricity (no ions)
• Small molecules
• Weak intermolecular forces, therefore:
• Low melting and boiling points

Question 9

How do intermolecular forces change as the mass/size of the molecule increases?

Answer 9

They increase. That causes melting/boiling points to increase as well (more energy needed to overcome these forces).

Question 10

What are polymers?

Answer 10

Polymers are very large molecules (>100s, 1000s of atoms) with atoms linked by covalent bonds.

Question 11

What are thermosoftening polymers?

Answer 11

Thermosoftening polymers - special type of polymers; they melt/soften when heated. There are no bonds between polymer chains. Strong intermolecular forces ensure that the structure is solid at room temperature. These forces are overcome with heating - polymer melts.

Question 12

What are giant covalent substances? Give examples

Answer 12

• Solids, atoms covalently bonded together in a giant lattice.
• High melting/boiling points - strong covalent bonds.
• Mostly don’t conduct electricity (no delocalised e^-)
• Diamond, graphite, silicon dioxide.

Question 13

Describe and explain the properties of Diamond

Answer 13

• four, strong covalent bonds for each carbon atom
• very hard (strong bonds)
• very high melting point (strong bonds)
• does not conduct (no delocalised electrons)

Question 14

Describe and explain the properties of Graphite

Answer 14

• three covalent bonds for each carbon atom
• layers of hexagonal rings
• high melting point
• layers free to slide as weak intermolecular forces between layers; soft, can be used as a lubricant
• conduct thermal and electricity due to one delocalised electron per each carbon atom

Question 15

Describe and explain the properties of Fullerenes

Answer 15

• hollow shaped molecules
• based on hexagonal rings but may have 5/7 - carbon rings
• C60 has spherical shape, simple molecular structure (Buckminsterfullerene)

Question 16

Describe and explain the properties of Graphene

Answer 16

• a single layer of graphite
• high melting and boiling points
• good electrical conductivity
• very strong bonds

Question 17

What is metallic bonding?

Answer 17

Forces of attraction between delocalised electrons and nuclei of metal ions.

Question 18

Describe properties of metals

Answer 18

• High melting/boiling points (strong forces of attraction)
• Good conductors of heat and electricity (delocalised electrons)
• Malleable, soft (layers of atoms can slide over each other whilst maintaining the attraction forces)

Question 19

What are alloys? Why are they harder than pure metals?

Answer 19

Alloys:

• mixtures of metal with other elements, usually metals
• different sizes of atoms distorts the layers, so they can’t slide over each other, therefore alloys are harder than pure metals

Question 20

Complete the table:

Answer 20

Question 21

What are the limitations of the simple model?

Answer 21

There are no forces between spheres and atoms, molecules and ions are solid spheres – this is not true

Question 22

What does the amount of energy needed to change state from solid to liquid or liquid to gas depend on?

Answer 22

The strength of the forces between the particles of the substance. The nature of the particles involved depends on the type of bonding and the
structure of the substance. The stronger the forces between the particles the higher the melting point and boiling point of the substance

Question 23

A pure substance will melt or boil at…? What about the mixture?

Answer 23

A fixed temperature.

A mixture will melt over a range of temperatures.

Question 24

What are the three states of matter?

Answer 24

Solid, liquid and gas