CHEM Exam 4

• Electron Domains

  Definition: Regions around an atom where electrons are likely to be found.

  Determination: Count the number of electron pairs (bonding and nonbonding) around a central atom.
• Bond Location


  Independent of dingle, double, or tripple bond
• VSEPR Model


  Valence Shell Electron Pair Repulsion

  
  

  1. Electron pairs - repel each other, whether they bond or not
  2. Electron pairs - placed far as possible form each other, we can predict shape of molecule
  3. Best arrangement of ED is that one that minimizes the repulsion among them.
• What are the 5 different arrangement pairs & Their angles?

  Linear (180°)

  Trigonal (120°)

  Tetrahedral (109.5°)

  Trigonal pyramid (>109.5°)
• Nonbonding pairs


  Repulsion is greater because they're physical large, and tends to compress bond angles
• What has larger electron domains than single bonds?

  Double & Triple bonds

  • Greater repulsion force making their bond angles greater
• what's this


  AB2 linear (180)

  
• what is this


  AB3 trigonal planar

  
• what is this


  AB4 tetrahedral

  
• what is this


  AB5 trigonal bipyramidal

  
• what is this


  AB6 octahedral

  
• What is Electron Domains?

  A region in which electrons are most likely to be found around an atom in a molecule or a solid
• Gas behavior

  no fixed shape or volume, take shape of container
• Boyle's Law

  Volume and Pressure Relationships

  "The volume of a fixed quantity of gas at constant temperature is inversely proportional to the pressure"
• Charles's Law

  Volume and Temperature

  "The volume of a fixed amount of gas at constant pressure is directly proportional to its absolute temperature (0 Kelvin)"
• Avogadro's Law

  Volume and Number of Moles

  "The volume of gas at constant temperature and pressure is directly proportional to the number of moles of the gas"
• What is the combined gas law?

  P1V1/n1T1 = P2V2/n1T2
• What is the Ideal Gas Law?

  PV = nRT
• What are the desired units of these values?

  P = atm

  V =

  n = moles

  R = atm x L / K x moles

  T = K
• What is the molecular geometry of 2 electron domains?

  • Linear
• What is the molecular geometry of 3 electron domains?

  • Trigonal planar
  • V-shape or Bent
• What is the molecular geometry of 4 electron domains

  • Tetrahedral
  • Trigonal pyramid or pyramidal
• What is the molecular geometry of 5 electron domains?

  • Trigonal bipyramid
  • Seesaw
  • T-shape
  • Linear
• What is the molecular geometry of 6 electron domains?

  • Octahedral
  • Square Pyramid
  • Square Planar
• What is electronegativity?


  The ability of an atom to attract electrons towards itself in a chemical bond
• Comparison of Bonds

  Single bond: One sigma bond

  Double bond: One sigma bond and one pi bond

  Triple bond: One sigma bond and two pi bonds
• Bonds

  Sigma bond: Single covalent bond; end-to-end overlap of atomic orbitals

  Pi bond: Second or third bond between atoms; side-by-side overlap of atomic orbitals
• Steric Number


  Calculation: Number of bonded atoms + Number of lone pairs
• Shape of Orbitals


  s: Spherical

  p: Dumbbell-shaped

  d: Complex and varied shapes

  
• Bond Polarity

  Calculation: ∆𝐸𝑁 = |Electronegativity of A - Electronegativity of B|

  Nonpolar bond (∆𝐸𝑁 ≤ 0.4)

  Polar covalent bond (∆𝐸𝑁 > 0.4)

  Polar Ionic bond (∆𝐸𝑁 ≥ 2.0)
• Molecular Polarity

  Determination: Sum of all dipole moment vectors

  Polar compound: All vectors add up

  Nonpolar compound: All vectors cancel out
• Molecular Geometry

  • Linear (2 electron domains)
  • Trigonal planar (3 electron domains)
  • V-shape or Bent (3 electron domains)
  • Tetrahedral (4 electron domains)
  • Trigonal pyramid or Pyramidal (4 electron domains)
  • Trigonal bipyramid (5 electron domains)
  • Seesaw (5 electron domains)
  • T-shape (5 electron domains)
  • Linear (5 electron domains)
  • Octahedral (6 electron domains)
  • Square pyramid (6 electron domains)
  • Square planar (6 electron domains)