• The differences in Pauling electronegativity values can be used to predict whether a bond is?covalent?or?ionic?in character

Electronegativity & covalent bonds

• Single?covalent?bonds?are formed by?sharing?a pair of electrons between two atoms
• In?diatomic?molecules?the electron density is shared equally between the two atoms
  • Eg. H₂, O_2?and Cl₂
• Both atoms will have the same electronegativity value and have an?equal?attraction?for the bonding pair of electrons leading to formation of a?covalent?bond
• The equal distribution leads to a?non-polar molecule

The electronegativity values are equal resulting in the formation of a nonpolar covalent bond

Electronegativity & ionic bonds

• When atoms of?different?electronegativities form a molecule, the shared electrons are not equally distributed in the bond
• The?more electronegative?atom (the atom with the higher value on the Pauling scale) will draw the bonding pair of electrons towards itself
• A molecule with partial charges forms as a result
• The?more electronegative?atom will have a?partial negative?charge (delta negative,?δ-)
• The?less electronegative?atom will have a partial positive charge (delta positive,?δ+)
• This leads to a?polar covalent molecule

The electronegativity values are not equal - polar bond forms

• If there is a?large?difference in electronegativity of the two atoms in a molecule, the least electronegative atom’s electron will?transfer?to the other atom
• This in turn leads to an?ionic bond?– one atom transfers its electron and the other gains that electron
  • The?cation?is a?positively charged species?which has?lost?(an) electron(s)
  • The?anion?is a?negatively charged species?which has?gained?(an) electron(s)

Large differences in electronegativity values lead to the formation of ionic bonds