mole - 6.02 x 10^23 representative particles of a substance and the SI unit for measuring the amount of a substance

Avogadro's number - the number of representative particles in a mole, 6.02 x 10^23

representative particle - the species present in a substance (usually atoms, molecules, or formula units)

molar mass - the mass of a mole of an element

Avogadro's hypothesis - equal volumes of gases at the same temperature and pressure contain equal numbers of particles

Standard temperature and pressure (STP) - a temperature of 0 degrees C and a pressure of 101.3 kPa, or 1 atmosphere (atm)

molar volume - the quantity, 22.4 L of a gas

percent composition - expresses the relative amounts of the elements in a compound with the percent by mass of each element in the compound

empirical formula - the basic ratio, which gives the lowest whole-number ratio of the atoms of the elements in a compound