Polarisation
- Created by: iloverevision:)
- Created on: 19-03-19 16:49
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- Electronegativity
- Polarisation
- Polar & Non-polar bonds
- covalent bonds in diatomic gases are non-polar because the atoms have equal electronegativities & so the electrons are equally attracted to both nuclei
- some elements such as carbon & hydrogen have similar electronegativities so bonds between them are essentially non-polar
- in a covalent bond between 2 atoms of different electronegativities, the bonding electrons are pulled towards the more electronegative atom
- the greater the difference in electronegativity the more polar the bond
- in a polar bond, the difference in electronegativity between 2 atoms is called a dipole
- a dipole is a difference in charge between 2 atoms caused by a shift in electron density in the bond
- Polar molecules
- if charge is distributed unevenly over a whole molecule then the molecule will have a permanent dipole
- molecules that have a permanent dipole are called polar molecules
- whether or not a molecule is polar depends on whether it has any polar bonds & its overall shape
- in simple molecules, such as hydrogen chloride, the 1 polar bond means charge is distributed unevenly across the whole molecule so it has a permanent dipole
- more complicated molecules might have several polar bonds
- shape of molecule decides whether or not it has an overall permanent dipole
- if the polar bonds are arranged symmetrically so that the dipoles cancel eachother out, such as in carbon dioxide, then the molecule has no permanent dipole & is non-polar
- if polar bonds are arranged so that they all point in roughly same direction & don't cancel eachother out, then charge will be arranged unevenly across the whole molecule
- this results in a polar molecule - the molecule has a permanent dipole
- shape of molecule decides whether or not it has an overall permanent dipole
- if charge is distributed unevenly over a whole molecule then the molecule will have a permanent dipole
- Polar & Non-polar bonds
- ability to attract bonding electrons in covalent bond
- measured on the Pauling scale
- higher number means element is better able to attract the bonding electrons
- fluorine is the most electronegative element.
- oxygen, nitrogen & chlorine are also very strongly electronegative
- Polarisation
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