A reaction that involves isomerization or decomposition of a single molecule. A standard for comparison in measurements. For example, the meter is a standard length which may be compared to any object to describe its length. The simplest arrangement of atoms or molecules that regularly repeats in a crystal structure. A universal indicator is an indicator which undergoes several color changes over a wide range of pH .
Universal indicators are usually mixtures of several indicators.
Compare with paired spin . A single electron occupying an orbital . An organic compound with molecules containing one or more double bonds. Compare with saturated fat . A lipid containing one or more carbon-carbon double bonds.