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
Orlando Magic his option for the 2010–11 season. They did the same for general manager Otis Smith, which would keep him in that position through the 2011–12 season. The Magic were without Rashard Lewis for the first 10 games of the 2009–10 season. Lewis tested positive for an elevated testosterone level that was caused by an over-the-counter supplement containing a substance banned by the league. To make matters worse, Vince Carter suffered a left ankle injury in just the second game of the season. Carter's injury turned out to be not too serious, but caused him to miss the next five games.