Astatine (At)

Unknown (presumed metallic)

Astatine is the rarest naturally occurring element on Earth, with less than 30 grams existing at any time, and as the heaviest halogen with [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵, astatine is so rare it has never been seen in bulk. Its longest-lived isotope (At-210) has a half-life of 8.1 hours and astatine-211 is being researched for targeted alpha therapy.

Key metrics

Density7g/cm³predicted

Melting point575Kpredicted

Boiling point610Kpredicted

Electronegativity2.2Paulingpredicted

Discovery

1940discovered

Discovered by: Dale R. Corson
Reactivity profile: Highly radioactive halogen
Reactivity: High
Bonding: Covalent

Electron configuration

\textcolor{#6b7280}{[Xe]}\; \textcolor{#a855f7}{4_{f}^{14}}\; \textcolor{#22c55e}{5_{d}^{10}}\; \textcolor{#ef4444}{6_{s}^{2}}\; \textcolor{#3b82f6}{6_{p}^{5}}

[Xe] 4f14 5d10 6s2 6p5

Wave function

\Psi_{\text{At}} \approx \frac{1}{\sqrt{85!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{85}(\mathbf{r}_{85}) \right|

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

Crystal structure

Face-Centered Cubic

Lattice constantsa = 1.00

Cell anglesα = β = γ = 90°

Coordination number12

Atoms per cell4

Atomic packing factor0.74

Physical properties

Atomic radius: 127 pmpredicted
Ionization energy: 920 kJ/molpredicted
Electron affinity: 270 kJ/molpredicted
Crystal structure: Face-centered cubic (fcc)

Oxidation statespredicted

-1+1+3+5+7

Acid/base

Can act as acid or base

Strongly acidicStrongly basic

State at 25 °CSolid

575 K610 K298 K

predicted

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

457.2nmAt I (blue)Blue100%

510.5nmAt I (green)Green60%

576.0nmAt I (yellow)Yellow40%

Dominant line 457.2 nmRange 457–576 nmTransitions 3