7A

• Lewis structures

  Show the bonds between atoms, but they leave out valuable information about the compounds they represent
• Bonding types

  • Single bonds
  • Double bonds
  • Triple bonds
• Molecular resonance

  A molecule that displays resonance does not oscillate between two or more possible electron configurations
• Expanded octets

  • Can only occur with period 3 and above elements
  • Situations where central atoms share more than 4 pairs of electrons
• Molecular orbital theory


  Determines the arrangements of electrons in the orbitals, tells chemists whether they will form single, double, triple bonds, & whether the formed bonds all have paired electrons
• Molecular orbital theory can be used to predict if a bond will form between two atoms
• sigma bond

  • strongest covalent bond due to overlap of orbitals
  • present in single bonds
  • the first bond formed
  • found in 1s orbitals
  • made from hybridized orbitals
• H2(hydrogen molecule)

  simplest diatomic molecule
• pi bonds

  • found in double and triple bonds (second, third, and so on)
  • found in p orbitals
• molecular orbital theory

  suggests that, the orbitals of a molecule's atoms are replaced by new orbitals when a molecule forms
• valence bond theory

  describes covalent bond formation and structure of molecules, why they have certain shapes
• octet exceptions

  • some molecules have an odd no. of valence electrons to share, in these cases one pair is short of one electron
  • other elements, such as boron, are content with less than 4 pairs of electrons
  • in a third group of molecules, more than 8 valence electrons are shared with a central atom
• expanded octets

  • situations where central atoms share more than 4 pairs of electrons
  • only possible with elements in periods 1-3
• antibonding orbitals

  • forms when atomic orbitals combine in an unfavorable manner
  • high in energy, more than the atomic orbital from which they form from
• bonding orbitals

  forms when electrons reinforce each other
• if electron waves interfere with each other, an orbital form outside of it, far from the 2 nuclei
• some orbitals encircle two or more atoms, often they encircle the entire molecule
• electrons from original atoms fill the least full shells first, then the next, and so on
• each molecule has a set of orbitals, equal to the sum of the atomic orbitals in the original atoms