Carbon ground state: 6 electrons

…

--- 2p (2 e-; 'up' spin) >>>>

- 2s (2 e-; opposite spin) >>>^ Valence e-

-1 s (2 e-; opposite spin)

C bondage 4 atoms "SP3"

C bondage 3 atoms "SP2"

C bondage 2 atoms "SP"

orbitals form tetrahedron in SP3

SP3 is a Sigma bond is an endwise overlap of a pair of orbitals

• 109 degrees between bond angles (nominal bond angle)
• Varies 5-10 degrees between various atoms.

SP2 Carbon (3 atoms bonded to the carbon)

• Trigonal shape
  • 3 lobes coming out
  • 120 degrees separation, with variation between molecules

• the 2p lobes (only one e- occupies this) come straight up & down; the trigonal forms a triangle
• forms sigma bond with oxygen between the SP2
• forms pi bond between the 2p orbitals
• forms sigma bonds between the hydrogen and the carbon
• H2C=O is formaldehyde; pi bond & sigma bond between the C & O
• 
  

SP Carbon bonded to 2 atoms

• 2P e-^e-^ unhybridized
• 2SP e-^e-^ hybridized
• 1s orbital
• 180 degrees apart
• H:C:::N:
  • sigma bond to hydrogen
  • sigma and 2 pi bonds to nitrogen
  • This is a Lewis Electron Dot design
    • H:C is one H e- and one C electron
    • C:::N is 3 from carbon and 3 from nitrogen (C total
    • N: is 2 electrons from nitrogen (total of 5 valence e-)

Lewis Electron Dot design

• contains all atom and all valence electrons
• methyl isocyanate
  • this is the Bhopal chemical
  • CH3NO

• Octet Rule
  1. first row elements have a max of 8 valence e- in a bonded state (includes "parent" & bonded atoms)
  2. Neon-like configuration
• Rules for doing the Lewis Formula
• x
  1. 
     

1. Start with a map (connectivity map)
2. Calculate total number of valence electrons;
   • 3(1) hydrogen
   • 2(4) carbon
   • 1(5) nitrogen
   • 1(6) oxygen
   • = 22
3. subtract number already in: 12 … 22-12=10
4. 14 needed (only have 10)
   • this implies double bonds
   • 2 double bonds needed.
   • now have H:H:H:C:N::C::O: with an extra pair of e- on nitrogen
     • note: H:H:H are all bonded directly to the C, not each other!
   • can also get H:H:HC:N:::C:O:::
     • this results in a + charge on the nitrogen and a - charge on the oxygen
     • Formal charge = group # - ([nonbond e-] + [#bonds to atom])
       • formally 0.5 of bonding e- belong to atom
       • eg N = 5-(0+4)= 1 charge
       • eg O = 6-(6+1) = -1charge
     • 
       

Misc info

Line Bond Formulas

• each 2e- bond is formed by a line (sigma or pi bonds)
• : represents non-binding electron pairs

::O::C::O::

Number of valence e- is equal to the group number (roman numeral at the top of the periodic chart)