October 23rd is being celebrated as "*Mole Day*" by chemists. A mole is a group of atoms or molecules which number 6.02 times 10 to the 23rd power. For any chemical element, there is 1 mole of atoms in the atomic mass of anelement when the mass is expressed in grams. Italian scientist Amedeo Avogadro is credited with determining this number. So on this date...10-23....from 6:02 this morning to 6:02 this evening, people are celebrating the contributions of Avogadro to the science of chemistry. Today, NPR talks with Art Logan, the president of the National Mole Day Foundation and a high school chemistry teacher in Clio (KLY-oh), Michigan, about Avogadro's number and the various ways chemistry students around the country are celebrating Mole Day.