Chemical substance identity of benzene, until the correct structure was described by Friedrich August Kekulé. Likewise, the idea of stereoisomerism – that atoms have rigid three-dimensional structure and can thus form isomers that differ only in their three-dimensional arrangement – was another crucial step in understanding the concept of distinct chemical substances. For example, tartaric acid has three distinct isomers, a pair of diastereomers with one diastereomer forming two enantiomers. An element is a chemical substance made up of a particular kind of atom and hence cannot be broken down or transformed by a chemical reaction into a different element, though it
Jeff Lewis (writer) Strikes Back" - Nominee<br> 1983: "Hill Street Blues" - David Milch, Jeffrey Lewis, Michael Wagner for "Gung Ho!" - Nominee<br> "'1984: "Hill Street Blues" - Teleplay by Jeffrey Lewis, Michael Wagner, Karen Hall, Mark Frost Story by Steven Bochco, Jeffrey Lewis, David Milch for "Grace Under Pressure"<br> 1984: "Hill Street Blues" - Teleplay by Jeffrey Lewis, Michael Wagner, David Milch, Mark Frost Story by Steven Bochco, Jeffrey Lewis, David Milch for "Parting Is Such Sweep Sorrow" - Nominee<br> 1985: "Hill Street Blues" - Teleplay by David Milch & Roger Director Story by Steven Bochco, Jeffrey Lewis, David Milch for "Watt