structure + bonding

What are the three states of matter?

solid, liquid and gas

What is the particle arrangement in a solid?

• fixed shape and volume

• cannot be compressed

• particles are close together and have no space to move

• solid particles vibrate constantly

What is the particle arrangement in a liquid?

• take the shape of their container

• particles are close together

• can move around each other

• cannot be compressed

What is the particle arrangement in a gas?

• particles move in all directions 

• particles sread out to completely fill their container

• can be compressed

• no flixed shape or volume

Why can gases be compressed?

because the particles are far apart

solid to liquid

melting

liquid to solid

freezing

solid to gas

sublimation

gas to solid

deposition

liquid to gas

boiling

gas to liquid

condensing

What is the melting point of ice?

0C

What is the boiling point of water?

100C

What is the freezing points of water?

0 degrees celcius

What is the condensation point of water vapour?

100 degrees celcius

What takes place at the melting point?

melting and freezing

What takes place at the boiling point?

boiling and condensing

What does the amount of energy needed to change state depend on?

the strength of the forces between the particles of the substance

What do stronger forces result in?

more energy needed to break the bonds

What happens to the temperature when the substance is undergoing a change of state?

it remains constant

What happens to the energy when something is melting or boiling?

all the energy from the surroundings is going towards breaking the forces between particles

What happens to the energy when something is condensing or freezing?

all the energy is transferred from the substance to the surroundings as stronger forces form between particles

What is an ion?

an atom that has lost or gained electrons to become postively or negatively charged

How is a positive ion formed?

when a metal atom loses electrons

Why does losing an electron form a positive ion?

because electrons have a negative charge, so when they get taken away, they are left with a more positive charge

How is a negative ion formed?

when a non metal atom gains electrons

Why does gaining an electron form a negative ion?

electrons have a negative charge, so an atom gaining an electron leads to a more negative charge overall

Why do atoms bond?

to gain a full outer shell of electrons

Why do atoms want to gain a full outer shell of electrons?

for stability

What is ionic bonding?

when electrons are transferred from one atom to another

What substances does ionic bonding take place with?

metal and non metals

How does ionic bonding work?

a metal atom donates an electron to a non metal atom, so that they can both have a (stable) full outer shell

What is electrostatic attraction?

the strong attraction between positive and negative ions

What is an ionic bond?

an electrostatic force of attraction between oppositely charged ions

What is an ionic substance?

a substance made of oppositely charged ions held in a fixed position by strong ionic bonds, held together in a giant ionic lattice

What is an ionic latice?

a giant 3d structure formed of millions of ions in an ionic compound packed together in a regular cubic arrangement, joined by ionic bonds.

How long will an ionic latice continue to build itself?

until there are no more ions left to add

What does giant mean in regards to ionic substances?

very large structure

What is lattice?

regular repeating arrangement

How are these ions held together in their lattices?

the opposite charges of the positively and negatively charged ions holds them together

What are the properties of ionic compounds?

• very high melting and boiling points

• can conduting electricity but not in a solid form

• brittle

• soluble in water

Why do ionic compounds have very high melting and boiling points?

the giant lattice structures are held together by strong electrostatic forces which require large amounts of energy to break

What is an example of an ionic compound having a high or low melting and boiling point?

• Sodium chloride has 1⁺ and 1^- ions while magnesium oxide has 2⁺ and 2^-

• There is a larger attraction between the stronger charges of MgO so more energy is needed

• Therefore magnesium oxide has an even higher melting and boiling point

What is needed for a substance to conduct electricity?

charged particles that are free to move and carry the charge

Why can’t solid ionic compounds conduct electricity?

ions in a solid state can’t move and movement is needed to conduct electricity

Why can molten/dissolved in water ionic compounds conduct electricity?

the ions are free to move and carry a charge

Why are ionic compounds brittle?

ions with the same charges are lined up together, so when a force is applied they slide against each other and snap

What substances does covalent bonding occur between?

non metals

What does covalent bonding involve?

a shared pair of electrons between atoms

Why do covalent bonds occur?

to achieve a full outer shell

How strong are covalent bonds?

very strong

How do you draw a dot and cross diagram?

When drawing Dot & Cross diagrams, we only draw the outer shell of electrons:

1. Fill up the outer shell of electrons by spacing the first four as far apart as possible, then pair the last four.

2. The electrons that are unpaired are the ones involved in the covalent bonding.

3. Re-arrange the electrons so the unpaired electrons are facing each other

4. Now join the two atoms together so that the unpaired electrons are being shared

What is a covalent compound?

compounds formed from non metals consisting of molecules

How are two or more atoms held together?

strong covalent bonds

How are molecules held together?

weak intermolecular forces

What are the two possible structures for covalent compounds?

• simple molecular structures

• giant covalent structures

What are examples of simple covalent molecules?

• water

• butane

• methane

• carbon dioxide

• oxygen

• hydrogen

What are the covalent bonds between atoms like in simple covalent structures?

strong covalent bonds between atoms

What are the covalent bonds between molecules like in simple covalent structures?

weak intermolecular forces

What are the melting and boiling points like for simple covalent molecules?

low melting and boiling point

Why do simple covalent molecules have a low melting/boiling point?

not a lot of energy is needed to overcome the weak intermolecular forces

What happens to the covalent bonds between atoms during melting?

they are not broken

Can simple covalent molecules conduct electricity?

no because there are no charged particles that are free to move and carry the charge

What are giant covalent structures?

millions of atoms joined together by covalent bonding

What are the bonds like in giant covalent structures?

very strong

What are the melting and boiling point like in giant covalent structures?

high

What is an allotrope?

structures that have the same chemical properties but different physical properties due to differences in structure and bonding

What are allotropes of carbon?

diamond and graphite

What does carbon form to achieve a full outer shell in diamond?

four covalent bonds

What is each carbon bonded to in diamond?

four other carbons, forming a giant covalent structure

What are some key properties of diamond?

hard and strng

What does carbon form in graphite?

three covalent bonds

What happens when covalent bonds are formed with graphite?

leaves on delocalised electron

Why can graphite conduct electricity?

delocalised electrons can move between the layers allowing it to conduct electricity

How does graphite arrange itself?

layers

What are the properties of graphite?

soft and slippery

What are the forces between ions called?

electrostatic forces

What are the forces between atoms called?

covalent bonds

What are the forces between molecules?

intermolecular forces

What type of structures are graphenes, fullerenes and nanotubes?

giant covalent structures

What is graphene?

single sheet of hexagonal rings of carbon atoms

How thick is grphene?

only one atom thick

Wht is graphene a single layer of?

graphite

What dimenson is graphene?

the worlds first 2d material

What are the properties of graphene?

• excellent thermal and electrical conductor

• very low density (lightweight)

• flexible

• transparent

• most reactive form of carbon

• very strong for its mass (over 200x stronger than steel)

What are the potential uses of graphene

• Quicker and more powerful computer chips, electric circuits and solar cells

• Flexible and durable electronic display screens

What is an allotrope?

a new form of an element

When was Buckminister Fullerene discovered?

1985

Have other fullerenes been discovered since?

Yes

What are the names of other fullerenes that have been made?

C₇₀, C₇₆ and C₈₄

What are fullerenes?

molecules of carbon atoms joined together to make hollow cages of different shapes, usually hexagonal rings of carbons atoms but can be pentagonal or heptgonal

What are Buckminister Fullerenes made of?

molecules of C₆₀

What bonds are between each carbon atom in a Buckminister Fullerene?

strong covalent bonds

How is each fullerene molecule attracter to each other?

weak intermolecular forces

How big is the fullerene molecule?

1nm in diameter

What are the uses of fullerene?

• Used as cages to trap smaller molecules inside them.

• Used to carry drug molecules around the body

• Used as lubricants - Fullerenes are spherical with weak intermolecular forces so can roll over each other

What are nanotubes?

hollow, culindrical tubws of carbon atoms

What are the properties of nanotubes?

• very strong/high tensile strength

• very good electrical and thermal conductors

What are the uses of nanotubes?

• can be used to reinforce materials like tennis rackents due to their strength

• can be used as catalysts because they have a large surface area to volume ratio