C2: Structure, Bonding and Properties of materials Flashcards
Ionic bonding(8):
- particles are oppositely charged ions
- occurs in compounds formed from metals combined with non metals
- high melting and boiling points (large amount of energy needed to break the bonds)
- DO NOT conduct electricity when solid ( ions are held in a fixed position in the lattice so they cannot move)
- DO conduct electricity when molten or dissolved (the lattice breaks apart and the ions are free to move)
Covalent bonds(4):
- particles are atoms that share pairs of electrons
- occurs in most non metallic elements and compounds of non metals
- can be small molecules e.g. ammonia
- can be giant covalent structures e.g. polymers
Metallic bonding(4):
- particles are atoms which share delocalised electrons
- occurs in metallic elements and alloys
- giant structure of atoms arranged in a regular pattern
- electrons in the outer shell of metal atoms are delocalised and free to move through the whole structure, this sharing of electrons leads to strong metallic bonds
What is an alloy?
A mixture of two or more elements at least one of which is a metal
Properties of alloys(2):
- harder than a pure metal because atoms of different sizes disrupt the layers so they cannot slide over each other
- high melting points due to strong metallic bonds
Metals as conductors(2):
- good conductors of electricity as they have delocalised electrons which carry electrical charge through the metal
- good conductors of thermal energy because energy is transferred by the delocalised electrons
State changes(3):
- Melting and freezing happen at the melting point
- boiling and condensing happen at the boiling point
- the amount of energy needed for a state change depends on the strength of forces between the particles in the substance
Ionic bonding in metals(2):
- Metal atoms loose electrons and become positively charged ions;
- group 1 metals form + 1 ions
- group 2 metals form +2 ions
Ionic bonding in non metals(3):
- non metal atoms gain electrons to become negatively charged ions
- group 6 non metals form -2 ions
- group 7 non metals form - 1 ions
Graphene(5):
- excellent conductor
- very strong
- a single layer of graphite is one atom thick
- contains delocalized electrons
- contains strong covalent bonds
Allotropes of carbon/ giant covalent structures(5):
- diamond, graphite and silicon dioxide
- very high melting points
- lots of energy needed to break their strong, covalent bonds
Properties of small molecules(6):
- covalent bonds in the molecule are strong but forces between molecules are weak
- LOW melting and boiling points(due to having weak intermolecular forces that are easily broken)
- DO NOT conduct electricity (due to them not having an overall electrical charge)
Properties of a polymer(4):
A polymer is a large molecule formed when lots of smaller monomer molecules join together
- solids at room temperature
- atoms are linked by strong covalent bonds
- high melting and boiling points
Diamond(7):
- each carbon atom is bonded to 3 others
- very hard
- high melting point
- DOES NOT conduct electricity
- rigid structure
- strong covalent bonds
- no delocalized electrons
Graphite/ layers of graphene(7):
- each carbon atom is bonded to three others, forming hexagonal rings with no covalent bonds between layers
- slippery
- very high melting point
- DOES conduct electricity
- layers can slide over each other
- strong covalent bonds
- delocalized electrons between layers
Fullerenes:
- hexagonal rings of carbon atoms with hollow shapes
Carbon nanotubes(7):
- very thin and long, cylindrical fullerenes
- very conductive
- high tensile strength
- large surface area to volume ratio
- used in the electronics industry
- reinforces composite materials
- work as catalysts and lubricants
Nanoparticles(8):
- between 1 and 100 nanometers(nm) in size ( 1 nanometer = 1x 10to the power of 9)
- uses; healthcare, cosmetics, sun cream, catalysts, deodorants and electronics
- nanoparticles May be toxic to people, they may also cause harm if they enter the brain or blood stream
Why is hydrogen chloride a gas at room temperature(3)?
- hydrogen chloride is a small molecule
- it has weak intermolecular forces
- which require a weak amount of energy to overcome
Why is chlorine more reactive than iodine?(3)
- reactivity decreases down the group
- the space between chlorine the nucleus and the electrons is bigger
- making it easier for chlorine to gain electrons
Polymer [definition]:
A large molecule that is made of many repeating subunits