Moles

So, what exactly is a mole in terms of chemistry? It isn't the skin feature you can find on many people and it also isn't the mammal, either.

In chemistry, a mole is a quantity equal to 6.02214076×10²³ of something. It's similar to a dozen, which is a quantity equal to 12 of something, or a pair, which is 2 of something.

The specific number 6.02214076×10²³ is known as Avogadro's Constant, often denoted N_A, and in units of 6.02214076×10²³/mol. So, why that specific number? Well, remember the atomic mass you see on elements in the periodic table? Those masses are technically given in atomic mass units(amu). However, Avogadro's Number makes it so that a mole of atoms(yes, that many!) is equal to the atomic mass in grams.

For example, 1 Caesium(Cs) atom has a mass of 132.91 amu. Avogadro's Number makes it so that 1 mole of Cs atoms(6.02214076×10²³ Cs atoms) has a mass of 132.91 grams. This is known as the molar mass of Caesium(132.91 g/mol) and the atomic mass of every element can be represented as the molar mass of that element, too. This means you can easily convert from moles of an element to the mass of that same element in grams using the molar mass, which makes it very helpful.

Note that for compounds, the molar mass of a compound is the sum of the molar masses of all its constituent elements. For example, the molar mass of water is double the molar mass of hydrogen plus the molar mass of oxygen, giving 2*1.01 + 16.00 = 18.02 g/mol.