This large number is a fundamental constant known as Avogadro's number (N A) or the Avogadro constant in honor of Italian scientist Amedeo Avogadro. A mole of substance is that amount in which there are 6.02214076 × 10 23 discrete entities (atoms or molecules). The mole provides a link between an easily measured macroscopic property, bulk mass, and an extremely important fundamental property, number of atoms, molecules, and so forth. One Latin connotation for the word “mole” is “large mass” or “bulk,” which is consistent with its use as the name for this unit. It provides a specific measure of the number of atoms or molecules in a sample of matter. The mole is an amount unit similar to familiar units like pair, dozen, gross, etc. This experimental approach required the introduction of a new unit for amount of substances, the mole, which remains indispensable in modern chemical science. Today, we possess sophisticated instruments that allow the direct measurement of these defining microscopic traits however, the same traits were originally derived from the measurement of macroscopic properties (the masses and volumes of bulk quantities of matter) using relatively simple tools (balances and volumetric glassware). However, because a hydrogen peroxide molecule contains two oxygen atoms, as opposed to the water molecule, which has only one, the two substances exhibit very different properties. For example, water, H 2O, and hydrogen peroxide, H 2O 2, are alike in that their respective molecules are composed of hydrogen and oxygen atoms. The identity of a substance is defined not only by the types of atoms or ions it contains, but by the quantity of each type of atom or ion. View available translations of the content. Download the content in PDF, Microsoft Word, or other format. Questions and Tasks Add a note to the content. Kinetic Molecular Theory, Real GasesĬontent Foreword Atoms Introduction Matter Measurement The Atom Periodic Table Moles & Mass Light Blackbody Radiation, Photoelectric Effect Atomic Spectra, Bohr Model Orbitals & Quantum Numbers Electron Configurations Periodic Trends Molecules Bonding Nomenclature Lewis Structures Part 1 Lewis Structures Part 2 Molecular Shape Polarity Organic Molecules Isomers Valence Bond Theory Molecular Orbital Theory Interactions Pressure & Gas Laws Combined & Ideal Gas Laws Dalton's Law, Graham's Law, Henry's Law Kinetic Molecular Theory, Real Gases Intermolecular Forces Properties of Water Applications of IMF Phase Diagrams Reactions Stoichiometry Limiting Reactants, % Yield % Composition, Empirical Formulas Energy, Heat, and Work Calorimetry Part 1 Calorimetry Part 2 Enthalpy Part 1 Enthalpy Part 2 Entropy Gibb's Free Energy Climate and Human Impacts Search within this publication Search the entire site Blackbody Radiation, Photoelectric Effect