Bonding, Structure & Properties of Matter

Question 1

What is ionic bonding?

Answer 1

Ionic bonding is there electristatic 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 point (strong electrostatic forces between oppositely charged 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 (give names of negative anions). What is important when working out a formula of an ionic compound?

Answer 4

E.g. Positive: Na+, Mg2+, Al3+, Ca2+, Rb+
E.g. Negative: Cl-, Br-, SO₄²⁻, NO⁻ ₃, OH- (chloride, bromide, sulfate, nitrate, hydroxide).
Ionic compounds are electrically neutral, i.e. positive and negative charges balance each other

Question 5

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

Answer 5

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 has 2 available outer shell electrons.
O is in Group VI, so can accept 2 electrons to get a full outer shell configuration.

Mg becomes Mg2+ and O becomes O2- (oxide)

Question 6

What is a covalent bond?

Answer 6

Covalent bond is a shared pair of electrons between two atoms

Question 7

Describe the structure and properties of simple molecular covalent substances

Answer 7

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

Question 8

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

Answer 8

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

Question 9

What are polymers? What are thermosoftening polymers?

Answer 9

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

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 10

What are giant covalent substances? Give examples

Answer 10

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 11

Describe and explain the properties of diamond

Answer 11

• 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 12

Describe and explain the properties of graphite

Answer 12

• three covalent bonds for each carbon atom
• laters of hexagonal rings
• high melting point
• laters 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 13

Describe and explain the porperties of fullerenes

Answer 13

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

Question 14

Describe and explain the properties of nanotubes and graphene

Answer 14

Nanotubes:
- cylindrical fullerene with high length to diameter ratio
- high tensile strength (strong bonds)
- conductivity (delocalised electrons)

Graphene - a single layer of graphite

Question 15

what is metallic bonding?

Answer 15

forces of attraction between delocalised electrons and nuclei of metal ions

Question 16

Describe properties of metals

Answer 16

• 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 17

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

Answer 17

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 18

describe the melting and boiling points of simple covalent bonds

Answer 18

low - because of weak intermolecular forces between molecules

Question 19

describe the melting and boiling points of ionic bonds

Answer 19

high - because of giant lattice of ions with strong forces between oppositely charged ions

Question 20

describe the melting and boiling points of giant covalent bonds

Answer 20

high - because of many strong covalent bonds between atoms in giant structure

Question 21

describe the melting and boiling points of metallic bonds

Answer 21

high - strong electrostatic forces between positive ions and delocalised electrons

Question 22

what is the conductivity when solid of simple covalent bonds

Answer 22

poor: no ions to conduct

Question 23

what is the conductivity when solid of ionic bonds

Answer 23

poor: ions can’t move

Question 24

what is the conductivity when solid of giant covalent bonds

Answer 24

diamond and sand: poor, because electrons can’tmove
graphite: good as free delocalised electrons between layers can move through structure

Question 25

what is the conductivity when solid of metallic bonds

Answer 25

good: delocalised electrons are free to move through structure

Question 26

what is the conductivity when molten of simple covalent bonds

Answer 26

poor: no ions

Question 27

what is the conductivity when molten of ionic bonds

Answer 27

good: ions are free to move

Question 28

what is the conductivity when molten of giant covalent bonds

Answer 28

poor

Question 29

what is the conductivity when molten of metallic bonds

Answer 29

good

Question 30

what is the general description of simple covalent bonds

Answer 30

mostly gases and liquids

Question 31

what is the general description of ionic bonds

Answer 31

crystalline solids

Question 32

what is the general description of giant covalent bonds

Answer 32

solids

Question 33

what is the general description of metallic bonds

Answer 33

shiny metal solids

Question 34

what are the limitations of the simple model?

Answer 34

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

Question 35

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

Answer 35

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. Ther stronger the forces between the particles the higher the melting point and boiling point of the substance

Question 36

A pure substance will melt or boil at…?

Answer 36

A fixed temperature.
A mixture will melt over a range of temperatures

Question 37

What are the three states of matter?

Answer 37

solid, liquid and gas

Question 38

What is nanoscience?

Answer 38

Science that studies particles that are 1 - 100nm in size

Question 39

State the uses of nanoparticles

Answer 39

• medicine (drug delivery systems)
• electronics
• deodorants
• sun creams (better skin coverage and more effective protection against cell damage)

Question 40

What are fine and coarse particles?

Answer 40

• Fine particles (soot), 100-2500 nm diameter
• coarse particles (dust), 2500-10^5 nm diameter

Question 41

Why do nanoparticles have properties different from those for the same materials in bulk?

Answer 41

high surface area to volume ratio