WebElements Periodic Table of the Elements | Astatine

Astatine: the essentials

The longest-lived isotope, ²¹⁰At, has a half-life of only 8.3 hours. There are about 20 isotopes known, all of which are radioactive. Astatine is a halogen and possibly accumulates in the thyroid like iodine.

Table: basic information about and classifications of astatine.
Name: Astatine Symbol: At Atomic number: 85 Atomic weight: [ 210 ] Standard state: solid at 298 K CAS Registry ID: 7440-68-8	Group in periodic table: 17 Group name: Halogen Period in periodic table: 6 Block in periodic table: p-block Colour: metallic Classification: Semi-metallic

This sample of uranite contains a vanishingly small amount of astatine. Image adapted with permission from Prof James Marshall's (U. North Texas, USA) Walking Tour of the elements CD.

Astatine: historical information

Astatine was discovered by Dale Corson, MacKenzie, Segre at 1940 in California, USA. Origin of name: from the Greek word "astatos" meaning "unstable".

Astatine ynthesized in 1940 by Dale Corson and others at the University of California, USA, by bombarding bismuth (²⁰⁹Bi) with α-particles.

Astatine: physical properties

Melting point: 575 [or 302 °C (576 °F)] K
Boiling point: 503 [or 230 °C (446 °F)] K
Density of solid: 6400 (estimated) kg m^-3

Ground state electron configuration: [Xe].4f¹⁴.5d¹⁰.6s².6p⁵
Shell structure: 2.8.18.32.18.7
Term symbol: ²P_3/2
Pauling electronegativity: 2.2 (Pauling units)
First ionisation energy: 920 kJ mol^-1
Second ionisation energy: no data kJ mol^-1

Isolation

Isolation: astatine is radioactive and essentially unavailable in nature. It is not possible to make other than in a nuclear reactor. Bombardment of the bismuth isotope ²⁰⁹₈₃Bi with α-particles (helium nuclei, ⁴₂He) results in formation of shortlived astatine and neutrons. The bismuth target is cooled during irradiation to prevent the volatile astatine disappearing.

²⁰⁹₈₃Bi + ⁴₂He → ²¹¹₈₅At + 2 ¹₀n

The ²¹¹At isotope has a half life of just over 7 hours so it is necessary to work quickly with it! Available quantities are of the order of 0.001 mg.

Heating the bismuth target to 300-600°C under N₂ results in a stream of the elemental astatine that can be collected on a cold glass finger.

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Astatine	Astate
Astat	Astaat
Astato	Astato
Astat	Astato

Astatine
- Essential data: names, symbol, atomic number, and atomic weight; block, period, and group in periodic table; description; standard state; registry number; and isolation
- History: meaning of name; discovery; and history of the element
- Uses
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Astatine around us
- Geology: Abundance of elements in the universe; the sun; meteorites; Earth's crust; oceans; and streams
- Biology: Abundance in humans; biological role; and health hazards)
Chemistry and compounds
- Compounds: halides, oxides, sulfides, hydrides, and complexes; lattice energies; and reduction potentials
- Reactions of astatine: reactions of astatine with air; water; halogens; acids; and bases
- Electronegativities: Pauling; Sanderson; Allred Rochow; Mulliken-Jaffe; and Allen
- Bond enthalpies of diatomic species
- Lattice energies
Element properties
- Physics properties: Boiling point; melting point; density; molar volume; thermal conductivity; and electrical resistivity; bulk modulus; critical temperature; superconductivity temperature; hardness (mineralogical, Brinell, and Vickers); linear expansion coefficient; Poisson's ratio; reflectivity; refractive index; rigidity modulus; Young's modulus; velocity of sound
- Crystal structure
- Thermochemistry: enthalpies of atomization, fusion, and vaporization; thermodynamic properties
- Pictures
Atom properties
- Electron shell properties: Electronic configuration; term symbol; electron affinity; ionization energies; and atomic spectra
- Atom sizes: atomic radius; Shannon and Pauling ionic radii; covalent radius; metallic radius; element bond length; and Van der Waals radius
- Atomic orbital properties: effective nuclear charge; electron binding energies; and valence orbital radii maxima
Nuclear properties
- Isotopes: isotope abundances; radioactive isotopes; isotope masses; nuclear spins; and nuclear magnetic moment
- NMR properties: frequencies; isotopes; magnetogyric ratios; quadrupole moments; receptivities; and relative sensitivities

Te	I	Xe
Po	At	Rn
Lv	Uus	Uuo

1	2															3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18

1 H																															2 He
3 Li	4 Be																									5 B	6 C	7 N	8 O	9 F	10 Ne
11 Na	12 Mg																									13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
19 K	20 Ca															21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
37 Rb	38 Sr															39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
55 Cs	56 Ba	57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb	71 Lu	72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
87 Fr	88 Ra	89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No	103 Lr	104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds	111 Rg	112 Cn	113 Uut	114 Fl	115 Uup	116 Lv	117 Uus	118 Uuo

Astatine

Astatine: the essentials

Astatine: historical information

Astatine: physical properties

Astatine: orbital properties

Isolation

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