| Question | Answer |
| Covalent bonding | When non-metals share electrons in order to gain a full outer shell. They must share the same amount as they want to gain |
| Covalent bonding is shown by | Dot and cross diagrams
- With one - representing a pair of shared electrons |
| Ionic bonding | The formation of ions through the loss or gain of electrons
Happens between metals and non-metals with the strong opposite attraction charge holding the bond together |
| Metallic bonding | Atoms lose their outer electron resulting in lots of positive charged atoms surrounded by a sea of delocalised electrons to prevent them from rebelling. |
| Properties of metallic bonding | Good conductors due to sea of delocalised electrons
Tough as lattice layers can easily slide over one another
Malleable and ductile as lattice layers can move |
| Diamond | A giant covalent structure.
4 bonds to each carbon resulting in a high m.p and b.p
Insoluble in water
Not conductible as no free electrons
Very strong as formed under lots of pressure and high temperatures |
| Graphene | 3 strong covalent bonds around each carbon so one delocalised electron.
Hexagonal layers held together by delocalised electrons
Weak inter-layer forces
High m.p and b.p
Layers can slide over each other so a lubricant
Conducts due to electron |
| Silica | Three oxygen bonded to a silicon atom with no free electrons
High melting and boiling point
Hard
Heat resistant so used as a fire retardant |
| Giant Ionic structures | Positive ions are surrounded by negative ions and vice versa
Strong attraction between + and - so high m.p and b.p
Soluble in water
Does not conduct when a solid, only when molten or a liquid
Brittle as like charges would be pushed together repelling |
| Simple molecular structures | Strong covalent bonds between atoms but weak intermolecular forces
Often liquid and gases
No free electrons so don't conduct
Do not dissolve in water |
| Alloys | Metals mixed with another element to disrupt pattern and so make it stronger
High-carbon steel is hard but brittle, a good conductor
Low-carbon steel is ductile, corrosive and a good conductor
Chromium steel is tough and corrosive resistant |
| Nano science | 1-100 nm small
Antimicrobial- Nano silver so used for medical stuff
Absorbs UV rays but stays transparent- Nano zinc oxide |
| Bucky balls | Buckminster fullerene are very strong due to it's covalent bonds
Unreactive and can penetrate cell walls
Used for drug administration
Environmental and health implications |
| Graphene | A single layer of graphite so very strong, flexible and a good conductor
Used for electronics and bulletproof vests |
| Fullerene | A nanotube made out of graphene
High length to diameter ratio so very strong
Used for bike frames |
| Properties to uses of Nano-technology (4) | -High conductivity-> micro electronics
-Strength -> Building materials enhancing
- High tensile strength-> Wires
- Light-> Overhead cables, sports equipment |
| Pros and Cons of nanotechnology | P- New properties so world of opportunity
N- Hard to track so unknown health and environmental impacts |
| Shape memory polymers | Remember shape when heated.
Uses- repairing wires |
| Shape memory alloys | Remember shape when heated but a metal
Uses- Orthodontic braces, stents, glasses frames |
| Thermochromic dyes | Changes colour wit heat
Uses- Thermometer, colour changing mugs |
| Photochromic dyes | Changes colour with light
Uses- T-shirts and glasses to sunglasses |
| Polymorph | Low melting point to be easily moulded
Uses- Gumshields |
| Hydrogels | Can shrink and swell by holding lots of water in it's polymer chains. Also responds to temperature and pH
Uses- nappies, absorbing toxic spillages |
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