Bond Theories 1 Lewis Structures Tell us about bonds in a molecule Do not tell us about the shape of the molecule Valence Bond Theory Based on the quantum model Says that covalent bonds form when orbitals of different atoms overlap sigma (?) ? the ends of the orbitals overlap pi (?) ? the sides of the orbitals overlap Types When Orbitals Overlap Bonds: sigma bond Single Bond s sublevel 5 Chemistry textbook, p. 162 sigma bond Single Bond p sublevel 6 Chemistry textbook, p. 162 Which type of bond forms first between covalently bonded atoms? Sigma Pi Depends on the atom Question 7 sigma and pi bond Double Bond 8 Chemistry textbook, p. 162 sigma and 2 pi bonds Triple Bond 9 Chemistry textbook, p. 162 pi bond forms only after a sigma bond weaker than a sigma bond double bond