6.2 Electronegativity and Polarity

Bee Brittain
Mind Map by Bee Brittain, updated more than 1 year ago
Bee Brittain
Created by Bee Brittain over 5 years ago
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AS - Level Chemistry (6 - Shapes of Molecules and Intermolecular Forces) Mind Map on 6.2 Electronegativity and Polarity, created by Bee Brittain on 04/15/2016.

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6.2 Electronegativity and Polarity
  1. Electronegativity
    1. Electronegativity is the ability of an atom to attract the bonding electrons in a covalent bond
      1. The bonded electron pair is shared evenly between to atoms unless...
        1. ... the nuclear charges are different
          1. ... the atoms may be different size
            1. ... the shared pair of electrons may be closer to one nucleus than the other
              1. If these conditions are met, the shared pair of electrons in the covalent bond may now experience more attraction from one of the bonded atoms than the other
              2. Ionic or Covalent?
                1. If the electronegativity difference is large, one bonded atom will have a much greater attraction for the shared pair than the other bonded atom.
                  1. The more electronegative the atom will have gained control of the electrons and the bond will now be ionic rather than covalent
              3. Bond Polarity
                1. Non-polar bonds
                  1. Bonded electron pair shared equally
                    1. Bonded atoms will be the same or the bonded atoms have the same/similar electronegativity
                      1. Pure Covalent Bond
                    2. Polar Bonds
                      1. Bonded pair shared unequally
                        1. A bond will be polar when the bonded atoms are different, or have a large difference in electronegativity
                          1. Polar Covalent Bond
                        2. A H-Cl bond is polarised as Cl atom is more electronegative than H
                          1. Due to it being polar, H has a slightly positive charge, where as Cl has a slightly negative charge (as it is the more electronegative one)
                            1. This separation of opposite charges is called a DIPOLE
                              1. A dipole in a polar covalent bond does not change and is called a permanent dipole to distinguish it from an induced dipole

                                Annotations:

                                • induced dipoles will be on my 6.3 Intermolecular Forces mind map
                        3. Polar Molecules
                          1. Depending on the shape of the molecule, the dipoles may reinforce one another to produce a larger dipole over the whole molecule, or cancel out if the dipoles act in opposite directions
                            1. A water, H2O molecule is polar
                              1. The two O-H bonds each have a permanent dipole
                                1. The two dipoles act in different directions but do not exactly oppose one another
                                  1. Overall the oxygen end of the molecule has a slightly negative charge and the hydrogen end of the molecule has a slightly positive charge
                                  2. A carbon dioxide, CO2 molecule is non-polar
                                    1. The two C=O bonds each have a permanent dipole
                                      1. The two dipoles act in opposite directions and exactly oppose each other
                                        1. Dipoles cancel out and the overall dipole is zero
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