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Element: Arsenic

General data

Element nameArsenic
Chemical symbolAs
Atomic number Z33
Year discoveredknown since antiquity
Standard state (25°C)Solid
CategoryMetalloid
Blockp
Atomic mass74.922
CPK color#BD80E3

Physical properties

Melting point1090 K (817 °C)
Boiling point887 K (614 °C)
Density5.776 g/cm³

Energy properties

First ionization energy9.815 eV
Electron affinity0.81 eV

Atomic structure

Protons33 (Atomic number)
Neutrons (As-75, most abundant isotope)42
Electrons33
Electron configuration[Ar] 4s² 3d¹⁰ 4p³
Oxidation states+5, +3, -3
Electronegativity (Pauling)2.18
Atomic radius (van der Waals)185 pm

Ionization energies - NIST ASD (33 states)

StateChargeIoniz. energy (eV)Type
As I0+9.78855 ± 0.00025measured
As II1+18.5892 ± 0.001measured
As III2+28.349 ± 0.012measured
As IV3+50.15 ± 0.06measured
As V4+62.77 ± 0.06measured
As VI5+121.19 ± 0.06measured
As VII6+147 ± 2calculated
As VIII7+180 ± 2.1calculated
As IX8+213 ± 2.2calculated
As X9+247 ± 2.2calculated
As XI10+296 ± 2.4calculated
As XII11+333 ± 2.5calculated
As XIII12+375 ± 3calculated
As XIV13+418 ± 3calculated
As XV14+460 ± 3calculated
As XVI15+587.6 ± 1.9semi-empirical
As XVII16+628.8 ± 0.6semi-empirical
As XVIII17+672.9 ± 0.9semi-empirical
As XIX18+728.9 ± 2.2semi-empirical
As XX19+774 ± 1.8semi-empirical
As XXI20+814 ± 4semi-empirical
As XXII21+911.7 ± 1.1semi-empirical
As XXIII22+956.79 ± 0.03semi-empirical
As XXIV23+2356.9 ± 1.4semi-empirical
As XXV24+2486 ± 4semi-empirical
As XXVI25+2626 ± 6semi-empirical
As XXVII26+2766 ± 21semi-empirical
As XXVIII27+2938 ± 3semi-empirical
As XXIX28+3088.1 ± 1.9semi-empirical
As XXX29+3287 ± 3semi-empirical
As XXXI30+3411.643 ± 0.007calculated
As XXXII31+14447.6799 ± 0.0025calculated
As XXXIII32+15028.9251 ± 0.001calculated

Value type as given by NIST ASD: measured - from evaluated experimental data; calculated - from ab initio calculations (mostly highly ionised atoms that have not been measured; for the simplest ones, e.g. H I, the calculation is more accurate than measurement); semi-empirical - from interpolation, extrapolation or another semi-empirical method.

Photos

Photo of the element: Arsenic (As)
© images-of-elements.com (CC BY 3.0)

Isotopes (30)

ANHalf-lifeDecay
As-6330< 43 nsp
As-643169.2 msEC/β⁺
As-6532130.3 msEC/β⁺
As-663395.77 msEC/β⁺
As-673442.5 sEC/β⁺
As-6835151.6 sEC/β⁺
As-693615.2 minEC/β⁺
As-703752.6 minEC/β⁺
As-713865.30 hEC/β⁺
As-723926.0 hEC/β⁺
As-734080.30 dEC
As-744117.78 dβ⁻
As-7542stable-
As-764326.24 hβ⁻
As-774438.79 hβ⁻
As-784590.7 minβ⁻
As-79469.01 minβ⁻
As-804715.2 sβ⁻
As-814833.3 sβ⁻
As-824919.1 sβ⁻
As-835014.1 sβ⁻
As-84513.2 sβ⁻
As-85522.023 sβ⁻
As-8653944 msβ⁻
As-8754480 msβ⁻
As-8855200 msβ⁻
As-8956unknownβ⁻
As-9057unknownβ⁻
As-9158unknownβ⁻
As-9259unknownβ⁻

Data sources

More about the data sources