exam 1

• atom isotopes: atoms of same element but different atomic mass (i.e. different # of neutrons)
• atomic number: # of protons in nucleus - defines the element & nuclear charge (positive charge)
• atomic orbitals: regions of space (wavefunctions) that describe E & location of electrons (e-density) at atoms (negative charge)
• electron distribution in atoms (& molecules) largely dictates molecular structure and chemical reactivity
• valence shell: outermost (highest E) occupied n shell of electrons given by row/period
• valence electrons: electrons in the valence shell that are involved in bonding and reactions
• pauli exclusion principle: each electron is described by a unique of 4 quantum numbers
• atom electronic configuration (Aufbau principle): filled orbital at atom build up electron configuration in atoms by filling lowest E orbitals first
• Hund's rule: in case of partially degenerate orbitals, the state of highest spin multiplicity is lowest E (minimize electron/electron repulsion)
• single bonds: sigma bonds
• double bonds: sigma bond + pi bond
• triple bond: sigma bond + 2 pi bonds
• UI= #C - (#H + #X)/2 + #N/2 + 1
• octet rule is not satisfied, it is reactive
• EN value for Hydrogen: 2.1
• EN value for Lithium: 1.0
• EN value for Berylium: 1.5
• EN value for Boron: 2.0
• EN value for Carbon: 2.5
• EN value for Nitrogen: 3.0
• EN value for Oxygen: 3.5
• En value for Fluorine: 4.0
• En increases across a period and decreases down a group
• change EN<0.5 = nonpolar covalent bond
• change EN = 0.5 - 1.9 = polar covalent bond
• change EN > 1.9 = largely ionic bonding
• Formal charge = VE - (B+D)
• resonance symbol : <->
• saturated atom: sp^3 hybridization, 4 sp^3 orbitals, tetrahedral, 109.5 degrees
• making one pi bond: sp^2, 3 sp^2 orbitals + 1 p-orbital, trigonal planar, 120 degrees
• making two pi bonds: sp, 2 sp orbitals + 2 p-orbitals, linear, 180 degrees
• formula structure: CH3CH3
• condensed: H3C-CH3
• special cases for hybridization:

  1. unfilled (empty or singly-occupied) orbitals will be p orbitals
  2. lone pair electrons adjacent to pi-systems will want to reside in p-orbitals to become part of the (conjugated) pi-system
• hydrocarbons:

  1. saturated
  2. alkanes (single C-C bonds)
  3. unsaturated
  4. alkenes (double C-C bond)
  5. alkynes (triple C-C bond)
  6. arenes (one or more benzene-like rings
• methane

  • molecular formula: CH4
  • condensed formula: CH4
• ethane:

  • molecular formula: C2H6
  • condensed formula: CH3CH3
• propane:

  molecular formula: C3H8

  condensed formula: CH3CH2CH3
• butane:

  • molecular formula: C4H10
  • condensed formula: CH3(CH2)2CH3
• pentane:

  • molecular formula: C5H12
  • condensed formula: CH3(CH2)3CH3