Chemistry: Structure and Properties 1
- Created by: Catherine
- Created on: 20-04-13 14:31
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- Chemsitry: Structure and Properties
- Giant Ionic Structures
- ionic compounds have giant structures
- strong electrostatic forces hold ions together
- they are solids at room temperature
- lots of energy is needed to overcome ionic bonds and melt the solid
- therefore ionic compounds have high melting and boiling points
- lots of energy is needed to overcome ionic bonds and melt the solid
- when an ionic compound has been melted, ions are free to move
- this allows them to carry electrical charge
- so molten ionic compound conducts electricity
- this allows them to carry electrical charge
- some ionic solids dissolve in water
- this is because water molecules can split up the lattice
- ions are free to move in solution
- so ionic compound solution conducts electricity
- ions are free to move in solution
- this is because water molecules can split up the lattice
- ionic compounds have giant structures
- simple molecules
- atoms within a molecule are held together by strong covalent bonds
- bonds only act within the molecule
- so simple molecules have very little attraction for one another
- bonds only act within the molecule
- substances made from simple molecules have low melting and boiling points
- this is because little energy is needed to break the weak intermolecular bonds
- they do not conduct electrical charge
- simple molecules have no overall charge so cannot carry charge
- simple molecular substances with the smallest molecules have the weakest intermolecular forces
- these are gases at room temperature
- larger molecules have stronger attractions
- these may be liquids at room temperature or solids with low melting points
- atoms within a molecule are held together by strong covalent bonds
- giant covalent structures
- it takes an enormous amount of energy to break these lattices
- so these substances have high melting points
- diamond
- regular 3D giant structure
- every carbon atom bonds to 4 other carbon atoms
- this makes diamond hard and transparent
- graphite
- each carbon atm bonds with 3 other carbon atoms
- giant, flat 2D layers
- no covalent bonds between layers
- so they slide over each other, making graphite slippery and grey
- no covalent bonds between layers
- graphite and fullerenes
- in carbon, the layers are flat sheets of hexagons
- one electron from each carbon atom is delocalised
- this allows graphite to conduct heat and electricity
- one electron from each carbon atom is delocalised
- fullerenes are large molecules formed from hexagonal rings of carbon atoms
- the rings join together to form cage-like shapes with different numbers of C aoms
- scientists are finding many uses for fullerenes
- e.g. drug delivery, lubricants, catalysts, reinforcing materials
- in carbon, the layers are flat sheets of hexagons
- it takes an enormous amount of energy to break these lattices
- Giant Ionic Structures
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