24 October 11

Yesterday (10-23) was Mole Day, honored by chemists worldwide because of the wondrous powers of Avogadro's Number, 6.022 X 10²³. That's a "6" followed by 23 digits, and it counts the number of atoms in one mole of any element, such as 12 grams of carbon or 16 grams of oxygen. It's also the number of molecules of H₂O in every 18 grams of water, which is a little more than one tablespoon in kitchen measurements. So the number of water molecules you drink from one can of soda is roughly 12,000,000,000,000,000,000,000,000!

October 23 also marks the birthday (in 1875) of Gilbert Lewis, famous for developing the idea of "shared electrons" in chemical bonds.