Covalent Bonds
      – Forms when 2 atoms share a pair of valence e-
   A. Types of Covalent Bonds
      1. Single Covalent Bond – two atoms share   one pair 
      of electrons
         Ex: F                             Unshared pair – e- not 
             2                             shared between atoms
    ●●    ●●                ●● ●●
                                            ●●    ●●
   ●  ● ●   ●              ●  ●  ●         ●        ●
   ● F    F●               ● F●F●     or   ● F    F●
    ● ●   ●●                ●● ●●           ●●    ●●
    What makes this bonding work?
    Atoms have 8 e- in their outer level to make them stable
              Covalent Bonds (cont.)
    Ex: H2
        ●   ●                 ●     or
       H     H              H●H          H H
                                    -
           Why does H only need 2 e to be stable?
                      2 
              first energy level only contains 2 e-
          Covalent Bonds (cont.)
    2. Double Covalent Bond – 2 pairs of electrons 
      are shared between atoms
      Ex: O2
      ●●       ●●          ●    ● ●    ●    ● ●
     ●  ●    ●   ●        ●  ● ●   or ●
     ●O       O●         ● O●● O      ●O    O●
      ●        ●          ●      ● ●   ●     ●
            Covalent Bonds (cont.)
      3. Triple Covalent Bond – 3 pairs of electrons 
        are shared between atoms
        Ex: N2
      ●●       ●●            ●
     ●  ●    ●   ●       ●   ● ●  ●   ●       ●
      N       N          ● N ● N● or ●N     N●
      ●        ●             ● ●
        Covalent Lewis Dot Structures
  1. Determine the # of valence e- in each atom in the 
   molecule
    (# valence e- = roman numeral for group A atoms)
  2. The central atom is often the first atom written & is 
   usually the atom with the least # of e-. (Exception – H 
   can’t be the central atom). This is going to be the 
   atom that needs to share the most electrons.