LECTURE recit

• Pi bonds


  Bonds where the orbitals line up next to each other and sort of overlap sideways
• Ethene's 3D molecular geometry

  • Trigonal planar
• 1 s-orbital + 1 p-orbital

  2sp orbital
• Carbon has 4 valence electrons
• Triple bonds

  • 1 sigma bond and 2 pi bonds
• Lewis structures


  Chemical structure with bonds as straight lines, lone pairs as dots, and atoms drawn out
• Methane's molecular shape

  • Tetrahedral
• Orbital overlaps in ethene

  • Ethene's carbons have 3 sp2 orbitals; 2 of the sp2 orbitals overlap with 2 hydrogen 1s orbital; 1 sp2 orbital overlaps with the other carbon's sp2 orbital. Additionally, the leftover p orbitals on the two carbons are close enough to produce a pi bond.
• Double bonds (according to valence bond theory)

  • 1 sigma bond and 1 pi bond
• Water's molecular shape

  • Bent
• Orbital hybridization


  The idea that one can mix two orbital shapes to make two hybrid atomic orbitals that look like both
• VSEPR electron pair geometries

  • Linear
  • Trigonal planar
  • Tetrahedral
  • Trigonal bipyramidal
  • Octahedral
• VSEPR theory


  Valence Shell Electron Pair Repulsion - The theory that the 3D shape of a molecule is determined by a central atom's lone pairs of electrons and the other atoms it's bonded to
• In ethene, each carbon needs to hybridize to 3 atomic orbitals to make 3 sp2 hybrid orbitals
• Hydrogen


  • 1s orbitals and 1 unpaired electron
• Orbitals


  Places where electrons are mostly found around atoms
• Constitutional isomers


  Also called structural isomers - Two molecules have the same number and types of atoms as each other but their connections are different
• Geometric isomers


  Have the same number and types of atoms and the same connections between them but differ in how the bonds are spatially arranged
• Understanding 3D molecular shapes is important because they determine the properties of the molecule
• If all of carbon's valence electrons are unpaired, there are 4 sp3 hybrid orbitals
• Sigma bond in methane


  • The overlap between each of the four hydrogen's 1s orbital and the single carbon's sp3 hybrid orbitals
• Triple bond 3D molecular geometry

  • Linear
• Major kinds of isomers

  • Constitutional
  • Geometric
• 1 s-orbital + 2 p-orbitals = 3sp2 orbitals
• 1 s-orbital + 3 p-orbitals = 4sp3 orbitals
• Isomers


  Molecules that have the same molecular formula but different arrangements of atoms
• Oxygen is often sp3 hybridized and forms single bonds in alcohols. But it can also be sp2 hybridized and form double bonds as a carbonyl group.
• Orbital names and shapes

  • s orbital: spherical
  • p orbital: dumbbell
  • d orbital: four-leaf clover (1st - 4th), elongated dumbbell with a doughnut in the middle (5th)
  • f orbital: too complex to describe