Ravi Patel Chapter 4,5 organic chemistry- The study of carbon & hydrogen compounds (organic compounds). Tetravalent- 4 electrons in valence shell, Ex. carbon Hydrocarbon- An organic molecule consisting only of carbon and hydrogen. Isomer- One of several compounds with the same molecular formula but different structures and therefore different properties. The three types are structural, geometric, and enantiomers. structural isomer- One or several compounds that have the same molecular formula but differ in the covalent arrangement of their atoms. (DIFFERENT SHAPE) geometric isomer- One of several compounds that have the same molecular formula and covalent bonds between atoms but differ in the spatial arrangements of their atoms owing to the inflexibility of double bonds