Pentavalent
carbon (Texas carbon): A carbon atom with five covalent
bonds. Sometimes called a Texas carbon because everything
(including, apparently the valence
of carbon) is "bigger in Texas". In most molecules
carbon can have at most eight valence
shell
electrons, allowing for a maximum of four covalent
bonds and/or lone
pairs. Exceptions are very rare. In general pentavalent
carbons are not acceptable in introductory organic
chemistry.
Carbon can have at most four covalent
bonds. "Starfish methane"
with its pentavalent
carbon is out of the question.
