Identify the molecule by fragmentation patterns. The parent peak, or the molecular ion peak, is the peak that depicts the ion of the molecule without fragmentation. It is useful for determining the structure connectivity of a compound, including functional groups. For example, the complementary of red is cyan. You should know the colors of the universal indicator: Red: very acidic Orange: acidic Yellow: weakly acidic Green: neutral Blue: basic Purple: very basic ultraviolet region pi-electron and non-bonding electron transition Every time you have a bond, the atoms in a bond have their atomic orbitals merged together to form molecular orbitals. A cursory understanding of ultraviolet UV spectroscopy and its association with conjugation will suffice. When things are shielded, the magnetic field is smaller and they have small chemical shifts and appear upfield to the right. NMR is nuclear magnetic resonance because the nuclear stands for protons; magnetic stands for the external magnetic field; the resonance stands for the absorption of radio waves.