Shapes of molecules and ions - 2
- Created by: Shannon
- Created on: 08-05-14 08:49
View mindmap
- Shapes of molecules and ions
- Electron pair repulsion theory
- The type of electron pairing affects how much repulsion is experienced
- Lone pair/lone pair bond angles are the biggest
- Lone pairs repel more than bonding pairs
- Bond angles between bonding pairs are reduced because they are pushed together by lone-pair repulsion
- The type of electron pairing affects how much repulsion is experienced
- Characteristic shapes
- 2 electron pairs on the central atom
- Linear
- e.g BeCl2
- Bond angle of 180
- Linear
- 3 electron pairs on central carbon
- No lone pairs
- Trigonal planar
- e.g BCl3
- Bond angle of 120
- Trigonal planar
- 1 lone pair
- Bent
- e.g CO2
- Bond angle of 120
- Bent
- No lone pairs
- 4 electron pairs on central atom
- No lone pairs
- Tetrahedral
- e.g CH4
- Bond angle of 109.5
- Tetrahedral
- 1 lone pair
- Trigonal pyramidal
- e.g NH3
- Bond angle of 107
- Trigonal pyramidal
- 2 lone pairs
- Bent
- e.g H2O
- Bond angle of 104.5
- Bent
- No lone pairs
- 5 electron pairs on central carbon
- Trigonal bipyramidal
- e.g PCl5
- Bond angles of 90 and 120
- Trigonal bipyramidal
- 6 electron pairs on central carbon
- Octahedral
- e.g SF6
- Bond angles of 90
- Octahedral
- 2 electron pairs on the central atom
- Carbon structures
- Carbon forms three allotropes
- Different forms of the same element in the same state
- Diamond
- Graphite
- Fullerenes
- Diamond
- The carbons in diamond are covalently bonded, with sigma bonds, to 4 other carbon atoms
- Atoms are arranged in a tetrahedral shape
- Crystal lattice structure
- Has a very high melting point
- Extremely hard
- Used in diamond-tipped drills and saws
- Good thermal conductor
- Vibrations travel easily through the lattice
- Graphite
- Carbon atoms are arranged in sheets of flat hexagons, covalently bonded with 3 bonds
- The 4th outer electron is delocalised
- The weak bond between layers are easily broken, so that the sheets can slide over each other
- Used in dry lubricant and in pencils
- Electrical conductors
- Delocalised electron free to move
- The layers are far apart in comparison to the length of the covalent bonds
- This means that it is less dense than diamond
- Used for strong, lightweight sports equipment
- This means that it is less dense than diamond
- Carbon atoms are arranged in sheets of flat hexagons, covalently bonded with 3 bonds
- Fullerenes
- Molecules of carbon shaped like hollow balls or tubes
- Each carbon atom forms 3 covalent bonds, leaving free electrons that can conduct electricity
- Because they are hollow, they can be used to cage other molecules
- Form around another molecule, trapping it inside
- Could be used to deliver a drug into specific cells of the body
- Nanotubes
- Single layer of graphite rolled into a hollow tube
- Very strong, due to covalent bonding
- Used to reinforce graphite and to make stronger, lighter bulding materials
- Can conduct electricity
- Used in circuits for computer chips
- Very strong, due to covalent bonding
- Single layer of graphite rolled into a hollow tube
- Carbon forms three allotropes
- Electron pair repulsion theory
Comments
No comments have yet been made