What is a mole?

A mole is defined as a unit used in chemistry to quantify the amount of substance. Specifically, one mole is equivalent to (6.022 \times 10^{23}) entities, which can be atoms, molecules, ions, or other particles. This value, known as Avogadro's number, allows chemists to count and convert between atomic scale quantities and macroscopic amounts that can be measured in the laboratory.

The concept of a mole is fundamental in stoichiometry, where it facilitates calculations involving chemical reactions and conversions between mass and number of entities. Because a mole relates directly to the number of particles in a given sample, it emphasizes the relationship between mass (measured in grams) and the number of particles (like atoms or molecules) in a substance.

Understanding the mole also clarifies how various other concepts in chemistry relate to one another, such as molarity in solution concentrations or the relationships in balanced chemical equations. This makes option B, which defines a mole as a grouping of atoms (correct in the broader sense that it can refer to any particles including atoms and molecules), an appropriate choice.