1/2-Bonding+Structure Flashcards
What type of elements does ionic bonding involve?
Metal and non-metal elements.
Why do atoms react together?
To get a full outer shell of electrons, giving them the electronic structure of a noble gas.
What does ionic bonding involve?
Metal atoms (1-3) lose electrons to form positive ions, non-metal atoms (6-7) gain electrons to form negative ions.
What type of elements does covalent bonding involve?
Non-metal elements.
What does covalent bonding involve?
Electrons are shared between non-metal atoms.
What are the properties of simple covalent structures?
Low melting/boiling points as there are weak intermolecular forces which are broken easily, rather than the strong covalent bonds holding the atoms together.
What are the properties of giant covalent structures?
All atoms are bonded with strong covalent bonds so high melting/boiling point.
Name the key points of diamond, a giant covalent structure.
Each carbon atom has 4 covalent bonds so very strong.
Has very high melting/boiling point.
Large number of covalent bonds so very hard.
Name the key points of graphite, a giant covalent structure.
Each carbon atom forms 3 covalent bonds, 1 electron delocalised.
Due to delocalised electrons it conducts electricity.
The delocalised electrons mean that each layer has weak intermolecular forces so can slide over on another.
Name the key points of silicon dioxide, a giant covalent structure.
Similar to diamond.
Each oxygen atom bonded to 2 silicon atoms.
Each silicon atom bonded to 4 oxygen atoms.
Very high melting/boiling point.
Name the key points of fullerenes.
Hexagonal rings of different numbers of carbon atoms covalently bonded together.
Not giant covalent structures, made of simple molecules.
What are fullerenes useful for?
- delivering drugs into the body
* nanotubes for reinforcing materials
What are the properties of giant ionic structures?
Regular structure, held together by strong electrostatic forces between oppositely charged ions.
High melting/boiling points.
Conduct electricity when molten/dissolved in a solution as charged ions free to move.
What type of elements are involved in metallic bonding?
Metal elements.
What is involved in metallic bonding?
A giant structure in which electrons in the highest energy level are delocalised. Produces regular arrangement of positive ions held together by electrostatic attraction and delocalised electrons.
What do delocalised electrons do in metallic bonding?
- hold atoms together in a regular structure
- allow atoms to slide over each other so metals can be bent/shaped
- can move around freely so metals conduct heat and electricity
How big are nanoparticles?
1-100 nanometres in size.
Properties of nanoparticles are different from same materials in bulk, for example…
- electrons can move through an insulating layer of atoms
- nanoparticles are more sensitive to light, heat and magnetism
- nanoparticles possess a high SA in relation to volume
How do you make nanocomposite materials?
By adding other materials to plastics (to make stronger, stiffer and lighter materials).
Where are nanocomposite materials already being used?
In the car industry and other being developed for medical/dental applications. Also used in energy storage, sunscreens, textile fibres etc.
What are smart materials?
A type of nanostructure that can be designed so they have specific properties (on the nanoscopic scale) or behave in a certain way when subjected to specific conditions.
What are the properties of Lycra, a smart material?
Stretchy material used to make clothing.
Lycra molecules have sections that make it both stretchy and rigid.
Has properties that stop it being damaged by sweat or detergents.
Ideal for sport clothing.
What are the properties of Kevlar, a smart material?
Artificial fibre used to make body armour.
Flexible, strong and tough.
Molecules pack closely together and bonds form between adjacent molecules, making it strong.
What are the properties of Gore-Tex, a smart material?
Artificial fabric that keeps rain out but lets sweat pass through.
Contains lots of pores that stop water droplets passing though but allows water molecules from sweat to pass out.
Waterproof, breathable fabric, ideal for outdoor/sports clothing.
