Basic Chemistry

• Formal Charges in Lewis Structures

  • # of e- from P.T - (unbonded e- + 1/2 (# of bonds))
  • all formal charges add up to the charge of the molecule
• Isomers

  • different molecules of the same molecular formula
  • atom and electron placement changes
• constitutional isomers: same molecular formula, but the connectivity of their atoms are different
• Octet Rule exceptions

  • Group 2A and 3A atoms can not have octets as parts of neutral molecules (incomplete octet)
  • expanded octets possible
• Resonance

  • some molecules can be described by more than 1 lewis structure
  • done by changing the arrangement of electrons
• Resonance structure (pts)

  • resonance structures are not real descriptors of molecules nor are they in equilibrium with each other nor are they isomers
  • the resonance hybrid is the true representation of the molecule
  • R.S. differ only in the locations of electrons
• Drawing Resonance structures

  • They are like Lewis structures, and follow all the rules of Lewis structures
  • resonance structures differ only in the positions of multiple bonds and unshared electron pairs
  • ATOMS AND SINGLE BONDS DO NOT MOVE