Bonding

states of matter ionic bonding (describing how it occurs, explaining high mpts & conduction, writing ionic formulae) metallic bonding (describing it, explaining high mpts & conduction, explaining alloys) covalent molecules ('overlapping circle' diagrams, explaining low mpt/bpt diamond & graphite fullerenes 2 calculations (nanoparticle surface area to volume ratio & bond energies) limitations of models

1. Solid to Liquid

2. Liquid to Solid

3. Liquid to Gas

4. Gas to Liquid

5. Solid to Gas

6. Gas to Solid

1. Melting

2. Freezing

3. Evaporation

4. Condensation

5. Sublimation

6. Deposition

Changes of state are..

physical changes because no new

substances are formed

Solids

Particles have low energy

Particles held in fixed position by forces

Particles vibrate but cannot move freely so solids keep their own shape / do not flow

Particles are close together so solids cannot be compressed

Liquids

Particles have more energy and move quite fast
Particles move freely so liquids flow

Particles are close together so liquids cannot be compressed

Gases

Particles have high energy so move very randomly

Very weak forces between particles so particles are far apart.

This means:
-gases can be compressed

-gases expand in all directions to fill their containers

Limitations of Particle Model

• Particles are shown as solid spheres

• It does not show weak forces between particles

• It does not show movement/speed of particles 

Bulk Properties

• ‘Bulk’ means the whole substance (all particles together)

Melting & boiling points and density are ‘bulk properties’ because they depend upon how all particles behave together

Ionic bonding

-attraction between oppositely charged ions

-occurs between metals and non-metals (name or formula of a compound has metal & non-metal = ionic)

Ionic bonding occurs because

metal atoms lose outer electrons to form + ions

non-metal atoms gain outer electrons to form - ions

the oppositely charged ions strongly attract each other

Ionic Charges - group:

1, 2, 3, 5, 6, 7

1. +1, Transfer/lose 1 electron

2. +2, Transfer/lose 2 electron

3. +3, Transfer/lose 3 electron

5. -3, Accept/gain 3 electrons

6. -2, Accept/gain 2 electrons

7. -1, Accept/gain 1 electrons

Example of ionic bonding question

Ca transfers 2 outer e to form Ca 2+

2 Cl each gain 1 e to form Cl -

Ca 2+ & Cl - ions strongly attract each other

Zn is…

+2

To work out the state (solid, liquid or gas) at room temperature,

compare room temperature

with each mpt & bpt:

-if room temperature is below mpt AND bpt: it has not even melted = solid

-if room temperature is between mpt & bpt: it has melted but not yet boiled = liquid

-if room temperature is above mpt AND bpt: it has melted and boiled = gas

Limitations of Ionic Models

2D Model: It only shows 1 layer of ions/does not show where the

other ions are
3-D model: It is not to scale/large gaps between ions

Dot & cross diagrams: Do not show the structure of the compound/how the ions are arranged

Predict Ionic formulae

This diagram has the same number of grey + (Li) & green – (iodine, I)

For every 1 x Li there is 1 x I

The formula is LiI

Structure of Metals

a giant lattice of positive metal ions

attracted to free (delocalised) electrons

Why can metals be Bent/shaped/stretched

into wires why are they soft?

metal atoms/ions are same size

layers are not distorted

layers slide

Why can metals conduct heat?

free (delocalised) electrons

move & transfer energy

through the structure

Why can metals conduct electricity?

Delocalised/free electrons

move & carry charge

through the structure

Why do metals have a high mpt/bpt?

giant lattice

lot of energy needed to break

strong metallic bonds

Pure metals are very soft/malleable (easily shaped) because:

atoms are the same size

layers not distorted

and can slide over each other

Pure metals have limited uses because…

-they aren’t strong (soft)

-Metals are made into alloys to make them harder and stronger

Alloys are…

mixtures of metals or a mixture of a metal & non-metal

eg carbon

Alloys are examples of a formulation because…

they are a mixture

designed as a useful product

Alloys are stronger than pure metals because:

other atoms are different size to original metal atoms

so layers of metal atoms are distorted

and cannot slide over each other

Why do molecules have low mpts and bpts?

simple molecules

little energy needed to break

weak intermolecular forces

Why do molecules not conduct

electricity?

no free electrons

to carry charge

through the structure

Diamond and Graphite are both

allotropes of carbon (different pure forms of the same element)

Diamond - description of structure

giant lattice of C atoms

each bonded to 4 others

by covalent bonds

Why does diamond have a High mpt?

giant lattice

lot of energy needed to break

strong covalent bonds

Why is diamond hard?

each C atom bonded to 4 others

by strong covalent bonds

atoms cannot move

Why does diamond NOT conduct electricity?

no free (delocalised) electrons

to carry charge through the structure

Uses of diamond (related to properties)

Drill bits (very hard, high mpt)

Cutting other diamonds (very hard)

Graphite - Description of

structure

giant lattice of C atoms

each bonded to 3 others

by covalent bonds

weak forces between hexagon layers

Why does graphite have a high mpt?

giant lattice

lot of energy needed to break

strong covalent bonds

Why is graphite soft?

weak forces between layers

so layers slide

Why does graphite conduct electricity?

Delocalised/free electrons

move & carry charge

through the structure

Graphite Uses (related

to properties)

Pencil “lead” (soft)

Lubricating machinery (slippery)

Electric motor contacts (conducts electricity)

What are fullerenes?

Hollow molecules of C atoms mainly arranged in hexagons (but

some include rings with 5 or 7 C atoms)

1st fullerene discovered:

Buckminsterfullerene (‘Buckyball’)

‘Buckyball’ contains…

60 C atoms covalently bonded into a

sphere of hexagons & pentagons

Why does Buckminsterfullerene have a low mpt/ bpt?

molecular structure/simple molecules

little energy needed to break

weak intermolecular forces

Why is Buckminsterfullerene slippery?

spherical shape

weak intermolecular forces

molecules can slide/roll

Why does Buckminsterfullerene conduct electricity?

Delocalised/free electrons

move & carry charge

through the structure

Carbon nanotubes are…

fullerenes in cylinder form

Why do Carbon Nanotubes have Relatively high mpt/bpt?

large molecules

lot of energy needed to break

strong covalent bonds

Why do carbon nanotubes resist stretching?

very long compared to their width

Uses of fullerenes

delivering drugs around the body (as they are hollow)

catalysts

strengthening other materials (as they do not break when

stretched)

electrical circuits

Surface Area to Volume Ratio

Surface Area / Volume

Energy Change

Bond breaking - Bond making

(Left - right)

Bond breaking (LHS) is..

endothermic (absorbs heat energy)

Bond making (RHS) is..

exothermic (gives out heat energy)

If overall energy change is negative

Exothermic

If overall energy change is positive

Endothermic

In terms of bonds, endothermic and exothermic reaction

Exothermic: Energy given out making new bonds > Energy needed (used) to make bonds

Endothermic: Energy given out making new bonds < Energy needed (used) to make bonds

Overall Exothermic

Overall Endothermic

Molecule size

molecules get larger

the weak intermolecular forces are stronger

more energy needed to break them

Examples of molecule size

group 7 mpt/bpt increase down the group

organic molecules getting longer

very long polymers compared to small molecules