Basic Bonding

1. Lewis Structers

  1. Total - # total valence electrons.
  2. Need - # of electrons needed to satisfy doublet/octet rule.
  3. Shared = Total - Needed (Number of electrons that participate in bonds)
# of bonds = Shared / 2
# of lone pairs = Shared - Total; #/2

Practice


  • Methane, CH4
    1. Total = C(1*4) + H(4*1) = 8
    2. Need = C(1*8) + H(4*2) = 16
    3. Shared = 16 - 8 = 8
    # bonds = 8/2 = 4
    # lone pairs = 8 - 8 = 0



  • Ammonia, NH3
    1. Total = N(1*5) + H(3*1) = 8
    2. Need = N(1*8) + H(3*2) = 14
    3. Shared = 14 - 8 = 6
    # bonds = 6/2 = 3
    # lone pairs = 8 - 6 = 2; 2/2 = 1




2. Formal Charge

Formal charge of an atom = (# valence electrons in ground state) - (# of valence electrons in bound state)
N atom in the ground state (as if found on the periodic table has 5 valence electrons.