Arsenic (As)

Gray metalloid

Arsenic is a toxic metalloid historically known as the 'king of poisons' and now used in semiconductor manufacturing, and with a half-filled 4p³ shell, arsenic has three allotropes: grey (metallic semiconductor), yellow (polyatomic As₄), and black (amorphous). Gallium arsenide (GaAs) is critical for high-speed electronics.

Key metrics

Density5.73g/cm³

Melting point1,090K

Boiling point887K

Electronegativity2.18Pauling

Discovery

-1250discovered

Discovered by: Ancient civilizations
Reactivity profile: Toxic reactivity
Reactivity: Medium
Bonding: Covalent

Electron configuration

\textcolor{#6b7280}{[Ar]}\; \textcolor{#22c55e}{3_{d}^{10}}\; \textcolor{#ef4444}{4_{s}^{2}}\; \textcolor{#3b82f6}{4_{p}^{3}}

[Ar] 3d10 4s2 4p3

Wave function

\Psi_{\text{As}} \approx \frac{1}{\sqrt{33!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{33}(\mathbf{r}_{33}) \right|

Probability density $|\Psi|^2$ across the As valence shell.

Crystal structure

Rhombohedral

Lattice constantsa 1.00 · b 1.00 · c 1.00

Cell anglesα = β = γ = 61.5°

Coordination number—

Atoms per cell—

Atomic packing factor0.53

Physical properties

Atomic radius: 114 pm
Ionization energy: 947 kJ/mol
Electron affinity: 78 kJ/mol
Crystal structure: Rhombohedral

Oxidation states

-3+3+5

Acid/base

Can act as acid or base

Strongly acidicStrongly basic

State at 25 °CSolid

1090 K887 K298 K

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

451.1nmAs I (blue)Blue100%

475.8nmAs IBlue60%

501.8nmAs I (green)Cyan40%

Dominant line 451.1 nmRange 451–502 nmTransitions 3