Emission - molecules in excited electronic states can loose energy by emitting light Chemiluminiscence in fireflies
Vibrational excitation: infrared IR Tutor Units in IR Wavelength = 10 -6 m wavenumber Units cm -1 Model the bond between two atoms as a “spring” attached to the two atoms; the spring can vibrate.
Organic Chemistry Chemistry of carbon-containing molecules Carbon: has four electrons and four valence orbitals, and so its compounds have neither too few electrons, requiring electron deficient structures, nor too many electrons resulting in excessive lone pair-lone pair repulsions can form compounds containing stable C-C bonds can form stable bonds with a number of elements Result: almost an endless range of compounds with elements bonded to C in straight chains, rings, branched chains and with single, double and triple bonds
Hydrocarbons Saturated hydrocarbons: all C - C bonds are single bonds Unsaturated hydrocarbons: C=C or C C bonds
Butane (C 4 H 10 ) and larger alkanes: linear or branched Isomers: same number of atoms, different arrangement iso-butane n-butane
Alkanes are considered to be non-polar since the electronegativities of C and H are similar Interaction between hydrocarbon molecules are due to London dispersion forces Strength of these interactions increase with the number of electrons; determines melting and boiling points