GLOBAL KNOWLEDGE ARK

Reference library

Foundations

Explore concepts, laws, equations and methods, with clear explanations of their use and sources. Choose an area of study or find a specific entry.

More filters

Reference entries

Showing 61–90 of 1709 reference entries

Physics · MeasurementElectric current

Current measures charge crossing a chosen surface per unit time.

DefinitionPhysicsElectric field and force

An electric field assigns force per unit test charge.

DefinitionPhysicsMagnetic force on a moving charge

Magnetic force depends on charge motion relative to the field.

ModelPhysicsOhm's law and its domain

A linear current-voltage relation requires suitable conditions.

Empirical findingPhysicsFirst law of thermodynamics

Keep the heat and work sign convention explicit in an energy balance.

ModelPhysicsSecond law: isolated-system entropy

Apply entropy increase to the whole isolated system.

ModelPhysics · ChemistryIdeal-gas equation of state

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

ModelPhysicsPhoton energy and frequency

One photon's energy is proportional to its frequency.

ModelPhysics · Mathematics & logicInvariant spacetime interval

Lorentz transformations preserve a combined space-time separation.

ModelPhysicsNewton's third law

Interaction forces act on different bodies in equal and opposite pairs.

ModelPhysicsAngular momentum and torque

Torque changes angular momentum about a specified origin.

ModelPhysicsHydrostatic pressure

Static fluid pressure rises with depth under gravity.

ModelPhysicsArchimedes' buoyancy principle

The hydrostatic upward force equals displaced-fluid weight.

ModelPhysicsMaxwell equations in free space

Four field equations connect electric and magnetic fields with charge and current.

ModelPhysicsSchrödinger time evolution

A quantum wavefunction evolves according to its Hamiltonian.

ModelPhysicsBorn position probability

A normalized wavefunction assigns probabilities to position intervals.

ModelPhysics · MeasurementElementary charge

The elementary charge has an exact SI numerical value.

DefinitionPhysics · MeasurementBoltzmann constant

The Boltzmann constant has an exact SI numerical value.

DefinitionMeasurement · Chemistry · PhysicsAvogadro constant

The mole is linked to a specified number of entities.

DefinitionMeasurement · PhysicsSI defining luminous efficacy

A specified frequency fixes the photometric SI reference.

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.

Model
DefinitionSource checked

Chemical bonds

Chemistry

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

Key knowledge

A chemical bond describes interactions that bind atoms or groups of atoms into a stable entity. The term includes covalent molecular bonds and bonding in ionic crystals; a substance need not consist of separate molecules to be bonded.

Conditions and scope

  • Bonding descriptions refer to the specified structure and conditions; they do not imply permanent attachment.
  • The cited IUPAC definition is the explicitly identified archived Gold Book version 2.3.3.
Sources · 3

References

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

  1. Gold Book, version 2.3.3: Chemical bond (CT07009)International Union of Pure and Applied Chemistry (IUPAC)Reference guideold.goldbook.iupac.orgRead source
  2. Siyavula2 sources
    1. Physical Sciences 10: Covalent bondingSiyavulaTextbook chaptersiyavula.comRead source
    2. Physical Sciences 10: Ionic bondingSiyavulaTextbook chaptersiyavula.comRead source

Evidence and review

IUPAC's definition and its molecular and ionic-crystal examples; not a quantitative bond-energy calculation.

2026-10-10 · English scope checked against the complete archived CT07009 entry. The current Gold Book endpoint was retrieval-limited.

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

Scope or convention differs

Shared-electron bonding and opposite-ion interactions in extended crystals.

An ionic lattice need not consist of discrete molecules.

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 · 1

    Linked statements

    • For a molecular Lewis diagram, total the atoms' valence electrons, adding electrons for negative charge and subtracting them for positive charge. A bond line represents a shared electron pair; dots can represent lone pairs. Place these electrons on a proposed atom connectivity and check the total charge and electron count. Hydrogen commonly has a duet, and many main-group centers an octet; odd-electron, electron-deficient and hypervalent species require exceptions.

    Shared electron-pair symbols describe a bounded localized representation of covalent bonding.

Entry detailsPermanent link to this entry ↗
Record identity
chem-chemical-bonds
Revision
core.1
Structured reference record
Essential core · first collection