C3 - Structure and Bonding Flashcards
Ionic Compound properties
- High melting and boiling points due to strong electrostatic forces of attraction between ions
- Do not conduct electricity as ions are fixed
- When melted or dissolved in water they conduct electricity as ions are free to move
- Dissolve easily one water and ions separate
What kind of atoms form ionic bonds
Metals and Non-metals
What kind of atoms form covalent bonds
non-metals
Properties of simple molecular covalent substances
- Low melting and boiling points as there are weak inter-molecular forces are needed to be broken, not covalent bonds
- As molecule gets bigger, melting and boiling points increase as strength of molecular forces increases
- Don’t conduct electricity as they are not charged and there are no free electrons or ions
What are polymers and how are they held together
Large molecules consisting of lots of small units linked together by strong covalent bonds to form a long molecule with repeating units.
Properties of Polymers
- Higher melting and boiling point than simple molecular substances as intermolecular forces between molecules are stronger
- Solid at room temperature
- However, intermolecular forces weaker than ionic or covalent bonds so they have lower boiling points than ionic or giant molecular compounds
Giant Covalent Structures Properties
- Very high melting and boiling points as strong covalent bonds between atoms
- Don’t conduct electricity as don’t contain charged particles (graphite is exception)
Properties of Diamond
- Made up of carbon atoms that form four covalent bonds. this makes diamond very hard
- Very high melting point as strong covalent bonds
- No free electrons or ions so doesn’t conduct electricity
Properties of graphite
- Each carbon atom only forms 3 covalent bonds. So there are no covalent bonds between layers so they’re held together weakly and are free to slide over each other which makes graphite soft and slippery - ideal lubricating material
- High melting point of covalent bonds in layers need lots of energy to break
- Only 3 out of 4 of carbon’s outer electrons used in bonds so each atom has a delocalised electron that allow graphite to conduct thermal energy and electricity
What is graphene and it’s properties
- A single layer of graphite
- one atom thick
- network of covalent bonds make it very strong and light
- contains delocalised electrons so can conduct electricity
Uses of graphene
- Used in electronics
* Added to composite materials to improve strength without adding much weight
What are Fullerenes
Molecules of carbon shaped like closed tubes or hollow balls and are made mainly of carbon atoms arranged in hexagons with some rings of 5 or 7 atoms
What is the Buckminsterfullerene
the first fullerene discovered (C60) a hollow sphere containing 20 hexagons and 12 pentagons
Uses of fullerenes
- Used to ‘cage’ other molecules as the structure forms around another molecule or atom. This could be used to deliver a drug into the body
- Huge surface area could make them good industrial catalysts if individual catalyst molecules are attached to fullerenes
What are carbon nanotubes
Cylindrical fullerenes with very high length to diameter ratios
Properties and uses of nanotubes
- Can conduct thermal energy and electricity
- High tensile strength (don’t break when stretched)
- Used in technology (nanotechnology)
- Used in electronics or to strengthen materials without adding weight (eg in tennis racket frames)
What are properties of metals
- Electrostatic forces of attraction are strong so compounds with metallic bonds have very high melting and boiling points
- Delocalised electrons can carry charge through metal so metals are good conductors of electricity and heat
How big are nanoparticles
they have a diameter of between 1nm and 100nm and have a high surface area to volume ratio
Uses of nanoparticles
- Large SA to volume ratio makes them good catalysts
- Fullerenes could be used to deliver drugs to places in the body
- some Can conduct electricity so can be used in tiny electric computers
- Silver nanoparticles have antibacterial properties so can be added to polymer fibres to make surgical masks and wound dressings. they can also be added to deodorants
- Used in cosmetics
- Used in suncreams as they have better skin coverage so more effective protection from suns rays
Disadvantages of nanoparticles
- Ways they affect the body aren’t fully understood
- Might damage cells if they get into body
- When washes away might damage environment
