Electronegativity and intermediate bonding

• Electronegativity is the relative tendency of an atom in a covalent bond in a molecule to attract electrons in a covalent bond to itself
• Electronegativity is measured on the pauling scale (ranges from 0-4)
• F, O, N and Cl are the most electronegative atoms
• The most electronegative element is fluorine (F) and it is given a value of 4.0
• Factors affecting electronegativity

  • Electronegativity increases across a period as the number of protons increases and the atomic radius decreased because the electrons in the same shell are pulled in more
  • It decreases down a group because distance between the nucleus and the outer electrons increases and the shielding of inner shell electrons increases
• Ionic and covalent bonding are the extremes of a continuum of bonding type. Differences in electronegativity between elements can determine where a compound lies on this scale
• A compound containing elements of similar electronegativity and hence a small electronegativity difference will be purely covalent
• A compound containing element of very different electronegativity and hence a very large electronegativity difference (> 1.7) will be ionic
• Formation of a permanent dipole - (polar covalent) bond

  • A polar covalent bond forms when th elements in the bond have different electronegativities (of around 0.3 to 1.7)
  • When a bond is a polar covalent bond it has an unequal distribution of electrons in the bond and produces a charge separation. (Dipole) delta positive and delta negative ends
• The element with the larger electronegativity in a polar compound will be the delta negative end

  + -

  H - Cl