Astato

Símbolo	At
Número atómico	85
Grupo	17 (Familia del flúor)
Período	6
Bloque	p
Clasificación	Semimetal

Apariencia	Unknown, probably metallic
Color	Plata

Número de protones	85 p+
Número de neutrones	125 n0
Número de electrones	85 e-

De Wikipedia, la enciclopedia libreEl astato es un elemento químico de la tabla periódica cuyo símbolo es At y su número atómico es 85. Es radiactivo y el más pesado de los halógenos. Se produce a partir de la degradación de uranio y torio. Es el elemento más raro de la corteza terrestre, ya que solo se encuentra en la cadena de desintegración de varios elementos más pesados. Todos los isótopos de la astatina son de vida corta; el más estable es la astatina-210, con una vida media de 8,1 horas. Nunca se ha reunido una muestra del elemento puro, porque cualquier ejemplar macroscópico se vaporizaría inmediatamente por el calor de su propia radiactividad.

Fase en STP	Sólido
Densidad	6.35 g/cm3
Peso atómico	210 u

Punto de fusión	575 K 301.85 °C 575.33 °F
Punto de ebullición	610 K 336.85 °C 638.33 °F
Entalpía de vaporización	30 kJ/mol

Electronegatividad (Escala de Pauling)	2.2
Afinidad electrónica	233 kJ/mol
Estado de oxidación	−1, +1, +3, +5, +7 ()
Energía de ionización	899.003 kJ/mol

Configuración electrónica Configuración abreviada	[Xe] 4f14 5d10 6s2 6p5
Configuración electrónica Configuración completa	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p5
Carta de configuración de electrones	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p5
Electrones por nivel	2, 8, 18, 32, 18, 7
Electrones de valencia	7
Electrones de valency	1
Modelo atómico de Bohr	Figura: Diagrama de capa del átomo de Astato (At).
Diagrama orbital 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 6s 6p

Descubrimiento

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

Descubrimiento de astato 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	Propiedades
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