12C’s molar mass is 12 grams, which represents the combined mass of 6.02 x 10 23 12C atoms. By standardizing the number of atoms in a sample of an element, we also get a standardized mass for that element that can be used to compare different elements and compounds to one another. However, it is quite useful if we apply it to other substances, especially elements. Scientists have then defined the molar mass of a substance as the mass of 6.02214076 x 10 23 units of that substance. Regardless of whether the substance is 12C, electrons, or gray squirrels, one mole represents the same number of each of these things.įigure 2: Carbon-12, with 6 protons and 6 neutrons, is the isotope that used to define one mole. Experiments counting the number of 12C atoms in a 12-gram sample have determined that this number is 6.02214076 x 10 23. The International Committee for Weights and Measures-a group that defines the metric system’s units of measurement (for more information, see our module on The Metric System)-defines one mole as the number of atoms in exactly 12 grams of carbon-12 ( 12C, Figure 2). The mole does more than represent a big number: It provides a key link for converting between the number (amount) of a substance, and its mass. Instead of being used for things we encounter in daily life, the mole is used by scientists when talking about enormous numbers of particles like atoms, molecules, and electrons-although the mole’s usefulness goes beyond being a helpful scientific term. Obviously, the mole is not a term we need for most things in daily life.
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