Gold Book Terms - A

'A' value A-factor \(A\)ab initio calculations ab initio quantum mechanical methods abatement  in atmospheric chemistryabeo- abiological abiotic abiotic transformation absolute activation analysis absolute activity \(\lambda\)absolute configuration absolute counting  in radioanalytical chemistryabsolute electrode potential absolute full energy peak efficiency absolute lethal concentration \(\text{LC}_{100}\)absolute lethal dose \(\text{LD}_{100}\)absolute photopeak efficiency absolute preconcentration  in trace analysisabsorbance matching  in spectrochemical analysisabsorbance \(A\)absorbed (spectral) photon flux density absorbed (spectral) radiant power density absorbed dose  of a substanceabsorbed dose \(D\) of radiationabsorbed electron coefficient  in in situ microanalysisabsorbed electrons  in in situ microanalysisabsorber absorptance \(\alpha\)absorption absorption coefficient absorption coefficient  in biologyabsorption cross-section \(\sigma\)absorption factor absorption intensity absorption line absorption pathlength  of a sample cellabsorption spectrum absorptivity abstraction abstraction process  in catalysisabundance sensitivity  in mass spectrometryac accelerating voltage scan \(\text{V}\) in mass spectrometryacceleration energy  in in situ microanalysisacceleration of free fall \(g\)acceleration \(a\)accelerator  in solvent extractionacceptable daily intake acceptor number \(\text{AN}\)accommodation coefficient accretion  in atmospheric chemistryaccuracy  of a measuring instrumentaccuracy  of measurementacenes acetals acetogenins acetonides acetylene black acetylenes acetylides Acheson graphite achiral achirotopic aci-nitro compounds acid acid anhydrides acid deposition  in atmospheric chemistryacid rain  in atmospheric chemistryacid thioanhydrides acid-labile sulfur acid–base indicator acid–base titration acidimetric titration acidity  of a mediumacidity constant acidity function acidosis actinic actinic flux \(S_{\lambda}\)actinism actinometer action spectrum activated adsorption process activated carbon activated charcoal activated complex activation activation analysis (nuclear) activation cross-section activation energy activation  in electrochemical corrosionactivation  in radiochemistryactivation reaction activator active centre active medium active metal  in electrochemical corrosionactive site  in heterogeneous catalysisactive solid active species active state  in electrochemical corrosionactive transport  in biologyactivity activity \(a\)activity coefficient \(f\),\(\gamma \)activity \(A\) of a radioactive materialacute toxicity acyl anions acyl carbenes acyl cations acyl groups acyl halides acyl radicals acyl shift (1,2-, 1,3-, photochemical) acyl species acylals acylium ions acyloins acyloxyl radicals added hydrogen addend addition addition reaction additive additive name additivity  of mass spectraadditivity principle adduct adduct ion  in mass spectrometryadhesional wetting adiabatic adiabatic electron transfer adiabatic ionization  in mass spectrometryadiabatic lapse rate  in atmospheric chemistryadiabatic photoreaction adiabatic transition-state theory adiabatic treatments of reaction rates adjacent re-entry model  in polymer crystalsadjusted retention volume adjuvant  in immunologyADMR adsorbate adsorbent adsorber adsorption adsorption capacity adsorption chromatography adsorption complex adsorption current adsorption hysteresis adsorption indicator adsorption isobar adsorption isostere adsorption isotherm  in chromatographyadsorptive advancement advection  in atmospheric chemistryadverse effect aeration  in atmospheric chemistryaerobe aerobic aerobic conditions aerogel aerometer  in atmospheric chemistryaerometric measurement  in atmospheric chemistryaerosol aerosol hydrolysis affine chain behaviour affinity chromatography affinity of reaction \(A\)after mass analysis  in mass spectrometryageing of precipitate  of precipitateagglomerate  in catalysisagglomerate  in polymer scienceagglomeration (except in polymer science) agglomeration  in polymer scienceagglutination aggregate  in catalysisaggregation (except in polymer science) aging  of a polymeraglycon agonist agostic agostic interaction agranular carbon air contaminant  in atmospheric chemistryair mass  in atmospheric chemistryair monitoring station  in atmospheric chemistryair pollutant air pollution air pollution index air pollution survey  in atmospheric chemistryair quality characteristic  in atmospheric chemistryair resource management  in atmospheric chemistryair sampling network  in atmospheric chemistryair-lift bioreactor Aitken particles albedo albumin alcogel alcoholates alcohols alcoholysis aldaric acids aldazines aldehydes aldimines alditols aldoketoses aldonic acids aldoses aldoximes alert levels  in atmospheric chemistryalicyclic compounds aliphatic compounds aliquot  in analytical chemistryalkalimetric titration alkaloids alkalosis alkanes alkanium ions alkene photocycloaddition alkene photodimerization alkene photoisomerization alkene photorearrangement alkenes alkoxides alkoxyamines alkyl groups alkyl radicals alkylenes alkylidene groups alkylideneamino carbenes alkylideneaminoxyl radicals alkylideneaminyl radicals alkylidenes alkylidynes alkynes allele allenes allo-  in amino-acid nomenclatureallometric allosteric enzymes allostery allotriomorphic transition allotropes allotropic transition allylic groups allylic intermediates allylic substitution reaction alternancy symmetry alternant alternating copolymer alternating copolymerization alternating current alternating voltage altocumulus cloud  in atmospheric chemistryaltostratus cloud  in atmospheric chemistryAM 0 sunlight AM 1 sunlight amalgam lamp ambident ambient air  in atmospheric chemistryambient air quality  in atmospheric chemistryambo Ames/salmonella test amic acids amide hydrazones amide oximes amides amidines amidium ions amidrazones aminals amine imides amine imines amine oxides amine ylides amines aminimides aminium ions aminiumyl radical ions amino radicals amino sugars amino-acid residue  in a polypeptideaminonitrenes aminooxyl radicals aminoxides aminoxyl radicals aminyl oxides aminyl radicals aminylenes aminylium ions ammonium compounds ammonium imines ammonium ylides ammoniumyl radical ions amorphous carbon amount concentration \(c\)amount fraction x (y for gaseous mixtures) amount of substance \(n\)amount-of-substance concentration amount-of-substance fraction \(x\)ampere \(\text{A}\)amperometric detection method  in electrochemical analysisamphipathic amphiphilic amphiprotic (solvent) ampholytes ampholytic polymer amphoteric amplification reaction amplitude of alternating current amplitude of alternating voltage anabolism anaerobe anaerobic anaesthetic analgesic analogue metabolism analogue to digital converter (pulse) analyte analytical function analytical instrument analytical intercomparison analytical portion analytical pyrolysis analytical quality control analytical radiochemistry analytical sample analytical solution analytical solution calorimetry analytical unit anation anchimeric assistance aneroid barometer Anger camera angle angle of observation angle of optical rotation \(\alpha\)angle strain angular distribution angular frequency \(\omega\)angular momentum \(L\)angular overlap model anhydrides anhydro bases anilides anils anion anion exchange anion exchanger anion radical anion-exchange polymer anionic polymer anionic polymerization anionotropic rearrangement anisometric anisotropy annelation annihilation  in photochemistryannulation annulenes annulenylidenes anode anodic transfer coefficient anomeric effect anomers ansa compounds antagonism antagonist antarafacial anthelmint(h)ic anthocyanidins anthocyanins anti anti-Compton γ-ray spectrometer anti-Hammond effect anti-Markownikoff addition anti-Stokes shift anti-Stokes type radiation (fluorescence) anti-thixotropy antiaromatic compounds antiaromaticity antibiotic antibody antibonding molecular orbital anticholinergic anticircular elution  in planar chromatographyanticlinal anticlined structures  in polymersanticodon anticyclone  in atmospheric chemistryantiferroelectric transition antiferromagnetic transition antigen antihelminth antimetabolite antimony–xenon lamp (arc) antimycotic antiparticle antiperiplanar antipodes antiprismo- antiresistant antiserum antisymmetry principle ap apex apex current apex potential aphicide apical (basal, equatorial) apicophilicity apo-  in carotenoid nomenclatureapoenzyme apoprotein apoptosis apparent (quantity) apparent lifetime apparent viscosity  of a liquidappearance energy appearance potential appearance temperature \(T_{\text{app}}\) in electrothermal atomizationapplied potential aprotic (solvent) aquagel aquation arachno- Archibald's method area  of an electrode-solution interfacearea of interface area viscosity areic arene epoxides arene oxides arenes arenium ions arenols arenonium ions argon ion laser arithmetic mean aromatic aromatic photocycloaddition aromaticity arrester  in atmospheric chemistryArrhenius A factor \(A\)Arrhenius energy of activation Arrhenius equation arsanes arsanylidenes arsanylium ions arsenides arsine oxides arsines arsinic acids arsinidenes arsinous acids arsonic acids arsonium compounds arsonous acids arsoranes artificial graphite artificial neural networks artificial radioactivity aryl cations aryl groups arylene groups aryne ascending elution  in planar chromatographyash  in atmospheric chemistryashing  in analysisaspirator assay assay kit association association reaction  in mass spectrometryassociative desorption associative ionization  in mass spectrometryassociative surface reaction asym- asymmetric asymmetric carbon atom asymmetric centre asymmetric destruction asymmetric film asymmetric induction asymmetric membrane asymmetric photochemistry asymmetric synthesis asymmetric transformation asymmetry asymmetry potential  of a glass electrodeatactic macromolecule atactic polymer atmosphere atmosphere  of the earthatmospheric pressure ionization  in mass spectrometryatom atom-atom polarizability atom-bond polarizability atom–molecule complex mechanism atomic charge atomic fluorescence atomic laser atomic mass constant atomic mass \(m_{\text{a}}\)atomic mass unit atomic number \(Z\)atomic orbital \(\psi\),\(\varphi\),\(\chi\)atomic ring-sector atomic spectral lines atomic symbol atomic units atomic weight atomization  in analytical flame spectroscopyatomization surface temperature \(T_{\text{s}}\) in electrothermal atomizationatomize atomizer  in analytical flame spectroscopyatropisomers attachment attenuance filter attenuance \(D\)attenuation attenuation coefficient atto attractive potential-energy surface attractive–mixed–repulsive classification attributable risk aufbau principle Auger effect Auger electron Auger electron spectroscopy Auger electron yield Auger yield autacoid auto-ionization  in mass spectrometryautocatalytic reaction automation  in analysisautomerization autophobicity autopoisoning  in catalysisautoprotolysis autoprotolysis constant autoradiograph autoradiolysis auxiliary electrode auxochrome auxotrophy avalanche photodiode average current density average degree of polymerization average life  in nuclear chemistryaverage rate of flow  in polarographyAvogadro constant \(N_{\text{A}}\),\(L\)avoided crossing  of potential-energy surfacesAvrami equation axial (equatorial) axial chirality axialite  in polymer crystalsaxis of chirality axis of helicity aza-di-π-methane rearrangement azacarbenes azamines azanes azenes azides azimines azines azinic acids azlactones azo compounds azo imides azo ylides azomethine imides azomethine oxides azomethine ylides azomethines azonic acids azoxy compounds azylenes α (alpha), β (beta) α-addition α-cleavage α-decay α-effect α-elimination α-oxo carbenes α-particle π-adduct σ-adduct