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Physics · ChemistryIdeal-gas equation of state

A simple gas model relates pressure, amount, volume and temperature.

ModelMeasurement · Chemistry · PhysicsAvogadro constant

The mole is linked to a specified number of entities.

DefinitionChemistryAtoms and elemental identity

The proton count of an atomic nucleus identifies its chemical element.

DefinitionChemistryIsotopes and mass number

Isotopes share a proton count but have different neutron counts.

DefinitionChemistryPeriodic organization of the elements

Atomic-number order reveals recurring patterns in electron structure and chemical properties.

ModelChemistryChemical bonds

Bonding describes interactions that bind atoms into molecules or extended structures.

DefinitionChemistry · MeasurementMole and amount of substance

The mole counts specified entities using the exact Avogadro constant.

DefinitionChemistryReaction stoichiometry

Balanced coefficients relate the amounts consumed and produced by a reaction.

MethodChemistryBalancing atoms and electric charge

A chemical equation must preserve each element's atom count and the total charge.

MethodChemistryDynamic chemical equilibrium

At equilibrium, opposing reactions continue without net composition change.

ModelChemistryBrønsted acids and bases

In the Brønsted description, an acid donates a proton and a base accepts it.

DefinitionChemistryGibbs energy and thermodynamic direction

Gibbs-energy change distinguishes thermodynamic favourability from reaction speed.

ModelChemistryReaction rates and empirical rate laws

Reaction rate measures change over time; a rate law describes its dependence under specified conditions.

MethodChemistryCatalysis and equilibrium

A catalyst changes the reaction pathway and rate, while preserving the equilibrium constant for the same reaction.

ModelBiology · ChemistryMetabolism and chemical pathways

Metabolism comprises the regulated chemical reactions of living systems.

DefinitionEarth & cosmos · Biology · ChemistryEarth's carbon cycle

Carbon moves through biological, oceanic, atmospheric and geological reservoirs.

ModelPhysics · ChemistryAtomic state labels and Pauli occupancy

Quantum labels specify orbitals and spin states.

ModelPhysics · ChemistryBloch states and electronic bands

A periodic crystal potential organizes energies by wavevector and band.

ModelPhysics · ChemistrySemiconductor electrons and holes

Band occupancy and doping control mobile carriers.

ModelChemistryElectron screening and effective nuclear attraction

Other electrons modify the attraction experienced by an electron in an atom.

ModelChemistryMultielectron ground-state configurations

Orbital occupations connect atomic electronic structure with valence chemistry.

ModelChemistryLocalized bonds and resonance descriptions

Localized orbital overlap and resonance are complementary chemical descriptions.

ModelChemistryMolecular orbitals and bonding occupation

A molecular orbital description distributes electronic states across a molecule.

ModelChemistryIntermolecular interactions

Dispersion, dipole interactions and hydrogen bonding influence molecular materials.

ModelChemistryBonding classes of solids

Ionic, metallic, molecular and network solids organize common bonding patterns.

DefinitionChemistryPolymers and macromolecular architecture

Polymers are substances composed of macromolecules with recurring structural units.

DefinitionChemistryCoordination compounds and ligands

Ligand donor atoms surround a central metal in a coordination sphere.

DefinitionChemistryActivities and chemical potentials

Activity expresses composition relative to a specified thermodynamic standard state.

DefinitionChemistrypH and hydrogen-ion activity

pH is an activity-based quantity realized through measurement conventions.

DefinitionChemistryBuffers and finite buffering capacity

An acid–base pair can resist limited changes in solution pH.

Model
DefinitionSource checked

Avogadro constant

MeasurementChemistryPhysics

The mole is linked to a specified number of entities.

Key knowledge

The Avogadro constant N_A is exactly 6.022 140 76 × 10²³ mol⁻¹ by the SI definition. An amount of one mole contains that number of specified elementary entities.

Reference values

N_A6.02214076e23mol⁻¹

Exact value · SI definition

Values and equations

N_A = 6.022 140 76 × 10²³ mol⁻¹

N_A
Avogadro constant mol⁻¹

Conditions and scope

  • Specify the entities being counted, such as atoms, molecules or ions.
  • Exact definition does not make a practical sample's amount or composition exact.
Sources · 5

References

Sources retain their recorded scope. A source link alone does not establish verification of every statement.

  1. Bureau International des Poids et Mesures (BIPM)3 sources
    1. SI defining constantsBureau International des Poids et Mesures (BIPM)Reference guidebipm.orgRead source
    2. The International System of Units, ninth edition, version 4.01 (2026)Bureau International des Poids et Mesures (BIPM)Reference guidebipm.orgRead source
    3. The International System of Units, 9th edition, version 4.01 (2026)Bureau International des Poids et Mesures (BIPM)Reference guidebipm.orgRead source
  2. Meet the ConstantsNational Institute of Standards and Technology (NIST)Reference guidenist.govRead source
  3. 国際単位系（SI）第9版 · Japanese translation, V3.01National Metrology Institute of Japan, AISTReference guide · PDFunit.aist.go.jpRead source

Evidence and review

BIPM constant table and SI Brochure mole definition; NIST Avogadro comparison.

2026-10-10 · Exact value, reciprocal-mole unit and specified-entity requirement only.

Foundational review

2026-10-10 · Fresh primary-source inspection of the complete compact record, including every statement, equation, quantity and material condition, followed by independent AI editorial review. This check does not certify all linked lessons or every passage of every cited publication.

Sources from other places

Agreement within this scope

Avogadro’s constant is exactly 6.02214076×10^23 mol−1 and the entities must be specified.

Entity counting and practical amount-of-substance determination still carry uncertainty.

Related reference entries

Explore relationships within this area of study and its connections to other areas.

Showing 1–1 of 1 relationships

Scientific relationships · 1 / 1

The relationship type describes the connection. Its linked statements, sources and conditions define the scope.

  1. Uses definition
    Relationship sources · 2

    Linked statements

    • Molar mass M is mass divided by amount of substance for specified entities and composition, so n = m/M. For entities with mean mass m_entity, M = NA m_entity. Since the 2019 SI revision, NA is exact but the atomic mass constant in kilograms is measured: the molar mass constant Mu = NA mu is close to, and no longer exactly, 0.001 kg/mol.

    M = NA m_entity uses the exact Avogadro constant with a specified mean entity mass.

Entry detailsPermanent link to this entry ↗
Record identity
si-avogadro-constant
Revision
core.1
Structured reference record
SI