Chem bio cc 10

• Opposites attract in magnets due to polarity and physics
• In polar molecules, opposite charges attract and positive and negative regions are drawn together
• Electronegativity


  The atomic property that helps us think about how much one atom will attract electrons in a bond, compared to other atoms
• Electronegativity can vary depending on the chemical compound an element is part of
• Pauling's electronegativity scale


  Ranks elements from most electronegative (fluorine) to least
• Electronegativity


  • Can tell us about atomic bonding (ionic, nonpolar covalent, polar covalent)
  • Can tell us about regions of charge in molecules
• Dipole


  A molecule with two regions of different charge
• Carbon dioxide is a nonpolar molecule because the electrons are being pulled away equally and symmetrically, despite the carbon-oxygen bonds being polar covalent
• 1. chloropropane is a slightly polar molecule due to the polar covalent carbon-chlorine bond
• Electron pushing/arrow pushing


  Precisely keeping track of electrons and how they move in chemical reactions
• Formal charge


  The difference between a neutral atom's valence electrons and the total electrons surrounding the atom in the molecule
• Resonance structures


  Different representations of a compound that differ in the placement of lone pairs and pi bonds
• Resonance hybrid


  The more stable blend of a molecule's resonance forms
• Identifying resonance structures


  1. Find a pi bond and an adjacent p orbital with 0, 1, or 2 electrons

  2. Whatever is at atom 1 moves to atom 3, and the stuff at 3 goes to 1

  3. Push electrons using curved arrows
• Guidelines for determining which resonance structures contribute more to the resonance hybrid

  • Neutral resonance forms are preferred
  • Keep an octet of electrons on oxygen and nitrogen
  • Negative charges are preferred on more electronegative elements, and positive charges are preferred on less electronegative elements