Astatine

Symbol	At
Atomic number	85
Group	17 (Fluorine group)
Period	6
Block	p
Classification	Metalloid

Appearance	Unknown, probably metallic
Color	Silver

Number of protons	85 p+
Number of neutrons	125 n0
Number of electrons	85 e-

From Wikipedia, the free encyclopediaAstatine is a very rare radioactive chemical element with the chemical symbol At and atomic number 85. It occurs on Earth as the decay product of various heavier elements. All its isotopes are short-lived; the most stable is astatine-210, with a half-life of 8.1 hours.

Phase at STP	Solid
Density	6.35 g/cm3
Atomic weight	210 u

Melting point	575 K 301.85 °C 575.33 °F
Boiling point	610 K 336.85 °C 638.33 °F
Heat of vaporization	30 kJ/mol

Electronegativity (Pauling Scale)	2.2
Electron affinity	233 kJ/mol
Oxidation states	−1, +1, +3, +5, +7 ()
Ionization energies	899.003 kJ/mol

Electron configuration Shorthand configuration	[Xe] 4f14 5d10 6s2 6p5
Electron configuration Full configuration	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p5
Electron configuration chart	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p5
Electrons per shell	2, 8, 18, 32, 18, 7
Valence electrons	7
Valency electrons	1
Bohr model	Figure: Shell diagram of Astatine (At) atom.
Orbital Diagram 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 6s 6p

Discovery

Dale R. Corson, Kenneth Ross MacKenzie, Emilio Segrè (1940)

Discovery of astatine Later in 1940, Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Segrè isolated the element at the University of California, Berkeley. Instead of searching for the element in nature, the scientists created it by bombarding bismuth-209 with alpha particles in a cyclotron (particle accelerator) to produce, after emission of two neutrons, astatine-211. The discoverers, however, did not immediately suggest a name for the element. The reason for this was that at the time, an element created synthetically in "invisible quantities" that had not yet been discovered in nature was not seen as a completely valid one; in addition, chemists were reluctant to recognize radioactive isotopes as legitimately as stable ones. In 1943, astatine was found as a product of two naturally occurring decay chains by Berta Karlik and Traude Bernert, first in the so-called uranium series, and then in the actinium series. (Since then, astatine was also found in a third decay chain, the neptunium series.) Friedrich Paneth in 1946 called to finally recognize synthetic elements, quoting, among other reasons, recent confirmation of their natural occurrence, and proposed that the discoverers of the newly discovered unnamed elements name these elements. In early 1947, Nature published the discoverers' suggestions; a letter from Corson, MacKenzie, and Segrè suggested the name "astatine" coming from the Greek astatos (αστατος) meaning "unstable", because of its propensity for radioactive decay, with the ending "-ine", found in the names of the four previously discovered halogens. The name was also chosen to continue the tradition of the four stable halogens, where the name referred to a property of the element.

Original word	astatos
Language of origin	Greek
Name source	Properties
Meaning	“Unstable”
Naming The name is derived from the Greek 'astatos', meaning unstable, because astatine has no stable isotopes and is the rarest naturally occurring element.

CAS Number	7440-68-8
ChemSpider ID	4573995
EC number	-
PubChem CID Number	5460480