The SI definition of the mole is the amount of a substance that contains as many entities as there are in exactly 12 g of carbon-12. Avogadro's number is 6.022 x 10 23 . One mole of anything is 6.022 x 10 23 units of that substance. The mass of 1 mole of an element is equal to its atomic mass in grams. Figure 3.4 Proceeding clockwise from the top, samples containing one mole each of copper, aluminum, iron, sulfur, iodine, and (in the center) mercury. 3.3 The MoLe 81 3.3 ~ The Mole Because samples of matter typically contain so many atoms, a unit of measure called the mole has been established for use in counting atoms. For our purposes, it is most convenient to define the mole (abbreviated mol) as the number equal to the number of carbon atoms in exactly 12 grams of pure 12c. Techniques such as mass spectrometry, which count atoms very precisely, have been used to determine this number as 6.02214 X 10 23 (6.022 X 10 23 will be sufficient for our purposes). This number is called Avogadro's
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