Element: Astatine

General data

Element name	Astatine
Chemical symbol	At
Atomic number Z	85
Year discovered	1940
Standard state (25°C)	Solid
Category	Halogen
Block	p
Atomic mass	[210]
CPK color	#754F45

Physical properties

Melting point	575 K (302 °C)
Boiling point	no data
Density	7 g/cm³

Energy properties

First ionization energy	9.5 eV
Electron affinity	2.8 eV

Atomic structure

Protons	85 (Atomic number)
Neutrons (At-210, longest-lived isotope)	125
Electrons	85
Electron configuration	[Xe] 6s² 4f¹⁴ 5d¹⁰ 6p⁵
Oxidation states	+7, +5, +3, +1, -1
Electronegativity (Pauling)	2.2
Atomic radius (van der Waals)	202 pm

Ionization energies - NIST ASD (85 states)

State	Charge	Ioniz. energy (eV)	Type
At I	0+	9.31751 ± 0.00008	measured
At II	1+	17.88 ± 0.02	semi-empirical
At III	2+	26.58 ± 0.05	semi-empirical
At IV	3+	39.65	semi-empirical
At V	4+	50.39	semi-empirical
At VI	5+	72 ± 2	calculated
At VII	6+	85.1 ± 2	calculated
At VIII	7+	130.1 ± 2.1	calculated
At IX	8+	149 ± 2.2	calculated
At X	9+	169 ± 2.2	calculated
At XI	10+	192.1 ± 2.4	calculated
At XII	11+	212 ± 2.5	calculated
At XIII	12+	236 ± 3	calculated
At XIV	13+	263 ± 3	calculated
At XV	14+	287 ± 3	calculated
At XVI	15+	311 ± 3	calculated
At XVII	16+	335 ± 3	calculated
At XVIII	17+	452 ± 22	calculated
At XIX	18+	481 ± 24	calculated
At XX	19+	510 ± 30	calculated
At XXI	20+	540 ± 30	calculated
At XXII	21+	600 ± 30	calculated
At XXIII	22+	630 ± 30	calculated
At XXIV	23+	720 ± 40	calculated
At XXV	24+	750 ± 40	calculated
At XXVI	25+	790 ± 40	calculated
At XXVII	26+	860 ± 40	calculated
At XXVIII	27+	920 ± 50	calculated
At XXIX	28+	990 ± 50	calculated
At XXX	29+	1050 ± 50	calculated
At XXXI	30+	1120 ± 60	calculated
At XXXII	31+	1180 ± 60	calculated
At XXXIII	32+	1250 ± 60	calculated
At XXXIV	33+	1320 ± 70	calculated
At XXXV	34+	1380 ± 70	calculated
At XXXVI	35+	1450 ± 70	calculated
At XXXVII	36+	1510 ± 70	calculated
At XXXVIII	37+	1590 ± 70	calculated
At XXXIX	38+	1650 ± 90	calculated
At XL	39+	1948 ± 4	calculated
At XLI	40+	2007 ± 4	calculated
At XLII	41+	2071 ± 4	calculated
At XLIII	42+	2139 ± 4	calculated
At XLIV	43+	2203 ± 4	calculated
At XLV	44+	2266 ± 4	calculated
At XLVI	45+	2373 ± 4	calculated
At XLVII	46+	2439 ± 4	calculated
At XLVIII	47+	2510 ± 4	calculated
At XLIX	48+	2576 ± 4	calculated
At L	49+	2841 ± 4	calculated
At LI	50+	2905 ± 4	calculated
At LII	51+	2977 ± 4	calculated
At LIII	52+	3042 ± 4	calculated
At LIV	53+	3312 ± 5	calculated
At LV	54+	3388 ± 5	calculated
At LVI	55+	3573 ± 5	calculated
At LVII	56+	3649 ± 3	semi-empirical
At LVIII	57+	5976 ± 6	calculated
At LIX	58+	6122 ± 6	calculated
At LX	59+	6279 ± 7	calculated
At LXI	60+	6445 ± 10	calculated
At LXII	61+	6604 ± 12	calculated
At LXIII	62+	6759 ± 15	calculated
At LXIV	63+	7068 ± 19	calculated
At LXV	64+	7230 ± 24	calculated
At LXVI	65+	7410 ± 30	calculated
At LXVII	66+	7570 ± 40	calculated
At LXVIII	67+	8030 ± 40	calculated
At LXIX	68+	8180 ± 50	calculated
At LXX	69+	8330 ± 50	calculated
At LXXI	70+	8480 ± 60	calculated
At LXXII	71+	9330 ± 60	calculated
At LXXIII	72+	9500 ± 70	calculated
At LXXIV	73+	9830 ± 90	calculated
At LXXV	74+	9990 ± 90	calculated
At LXXVI	75+	21210 ± 100	calculated
At LXXVII	76+	21600 ± 110	calculated
At LXXVIII	77+	22030 ± 120	calculated
At LXXIX	78+	22420 ± 120	calculated
At LXXX	79+	25580 ± 140	calculated
At LXXXI	80+	26090 ± 150	calculated
At LXXXII	81+	26730 ± 160	calculated
At LXXXIII	82+	27139 ± 0.4	calculated
At LXXXIV	83+	107930 ± 0.4	calculated
At LXXXV	84+	109887.2 ± 1.5	calculated

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: Astatine (At) — © images-of-elements.com (CC BY 3.0)

Isotopes (39)

A	N	Half-life	Decay
At-191	106	1.7 ms	α
At-192	107	88 ms	α
At-193	108	28 ms	α
At-194	109	286 ms	α
At-195	110	309 ms	α
At-196	111	377 ms	α
At-197	112	388 ms	α
At-198	113	4.47 s	α
At-199	114	6.97 s	α
At-200	115	43 s	α
At-201	116	85 s	α
At-202	117	184 s	EC/β⁺
At-203	118	7.4 min	EC/β⁺
At-204	119	9.2 min	EC/β⁺
At-205	120	26.9 min	EC/β⁺
At-206	121	30.5 min	EC/β⁺
At-207	122	1.81 h	EC/β⁺
At-208	123	1.63 h	EC/β⁺
At-209	124	5.42 h	EC/β⁺
At-210	125	8.1 h	EC/β⁺
At-211	126	7.216 h	α
At-212	127	314 ms	α
At-213	128	124 ns	α
At-214	129	558 ns	α
At-215	130	37 μs	α
At-216	131	0.30 ms	α
At-217	132	32.6 ms	α
At-218	133	1.28 s	α
At-219	134	56 s	α
At-220	135	3.71 min	β⁻
At-221	136	2.3 min	β⁻
At-222	137	54 s	β⁻
At-223	138	50 s	β⁻
At-224	139	1.3 min	β⁻
At-225	140	unknown	β⁻
At-226	141	unknown	β⁻
At-227	142	unknown	β⁻
At-228	143	unknown	β⁻
At-229	144	unknown	β⁻

Data sources

PubChem Periodic Table API - Retrieved on 29 June 2026 - licence: CC0
IUPAC CIAAW - Abridged Standard Atomic Weights 2024 - Table version: 2024 - licence: Public domain
NNDC Wallet Cards 2023 - Data as of 15 October 2024 - licence: Public domain
Images of Elements - Retrieved on 29 June 2026 - licence: CC BY 3.0

More about the data sources