Astatine is a short-lived radioactive element studied in extremely small quantities. Its chemistry has been compared experimentally with that of iodine and other halogens. It has no assigned standard atomic weight, and the limited material available makes measurement evidence especially important when describing its properties.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
Why does astatine targeting research need evidence about the chemical attachment?
Astatine-211 attached to targeting molecules
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Distinguish carrier from isotope
Astatine-211 is investigated with targeting molecules. The molecule’s targeting role and the isotope’s radioactive role are separate contributions that must remain connected for the intended concept.
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Why is isotope identity insufficient to establish selective delivery?
Atomic identity, reference properties and structure models
INTERACTIVE 3D85 visible sites
An electron censusDrag to rotate · scroll or pinch to zoom
[Xe] 4f14 5d10 6s2 6p5. Grouping electrons by principal shell connects the neutral-atom configuration to periodic-table patterns.
What this representation means
A three-dimensional counting diagram. Dots are count markers, not measured electron positions; spherical placement and spacing are arbitrary. There are no electron trajectories here. Orbitals describe quantum states.
Element 85 was sought through several premature claims before Dale Corson, Kenneth MacKenzie and Emilio Segrè established it at Berkeley in 1940. They identified an artificially produced radioactive element and investigated its chemical behavior. The eventual name, astatine, refers to instability. Its discovery emphasizes the difference between a suggestive signal and an identification supported by both nuclear observations and chemical evidence.
1940
Synthesis and identification
The Berkeley team establishes element 85.
2013
Ionization potential measured
CERN researchers report the first measurement of astatine’s ionization potential.
Tiny, transient amounts of astatine arise in natural radioactive chains, but they do not provide a practical stock of the element. Research material is produced artificially in accelerators. Every known is radioactive, so availability is tied to production and decay rather than to a recoverable deposit of astatine .
Astatine belongs to the halogens, yet its scarce, radioactive samples make straightforward comparisons with iodine difficult. Much of its chemistry is investigated at trace concentrations. Researchers study which chemical forms persist and how atoms attach to molecules; proposed bulk appearance and other unmeasured material properties should remain separate from these observations.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
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Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
solid
293.15 K, 101.325 kPa
Melting point in K
575 K
at standard pressure unless noted Estimated; astatine has never been isolated in bulk.
Boiling point in K
610 K
101.325 kPa
Density
Not recorded
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity in Pauling
2.2 Pauling
Pauling scale
First ionization energy in kJ/mol
899 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
150 pm
single-bond covalent radius
Common oxidation states
-1, +1
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust
Not recorded
upper continental crust, mass fraction
Has stable isotopes
Noderived
Discovery year in CE
1940 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 6
At 2.2 Pauling · Astatine
Electronegativity across period 6. Exact values.
Cs
0.79
Ba
0.89
La
1.1
Ce
1.12
Pr
1.13
Nd
1.14
Sm
1.17
Eu
1.2
Gd
1.2
Tb
1.1
Dy
1.22
Ho
1.23
Er
1.24
Tm
1.25
Yb
1.1
Lu
1.27
Hf
1.3
Ta
1.5
W
2.36
Re
1.9
Os
2.2
Ir
2.2
Pt
2.28
Au
2.54
Hg
2
Tl
1.62
Pb
2.33
Bi
2.02
Po
2
At
2.2
Electronegativity down group 17
At 2.2 Pauling · Astatine
Electronegativity down group 17. Exact values.
F
3.98
Cl
3.16
Br
2.96
I
2.66
At
2.2
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
