Why is the mole significant in chemistry?

The mole is significant in chemistry because it is a fundamental unit used to measure the amount of substance, equivalent to approximately 6.022 x 10^23 particles, which is known as Avogadro's number. This large number allows chemists to deal with the extremely small scale of atoms and molecules in a manageable way.

Using the mole provides a bridge between the atomic scale, where individual atoms and molecules exist, and the macroscopic scale, where we can measure out substances for reactions and calculations in grams or liters. The consistency and universality of the mole make it crucial for calculating quantities of reactants and products in chemical reactions, enabling the stoichiometric relationships that are fundamental to the practice of chemistry.

The other options do not accurately reflect the role of the mole. The mole is not a measure of volume, nor is it exclusively applicable to gases; it applies to solids, liquids, and gases alike. Additionally, the mole does not indicate the atomic mass of an element, which is a separate concept related to the mass of an individual atom rather than its quantity in moles.