Symbol	Ac
Atomnummer	89
Gruppe	3 (Scandiumgruppe)
Periode	7
Blok	d
Klassifikation	Actinid

Udseende	-
Farve	Sølv

Antal protoner	89 p+
Antal neutroner	138 n0
Antal elektroner	89 e-

Fra Wikipedia, den gratis encyklopædiActinium (af græsk; actinos, "stråle") er det 89. grundstof i det periodiske system, og har det kemiske symbol Ac: Under normale temperatur- og trykforhold optræder dette actinid som et stærkt radioaktivt sølvhvidt metal. Actinium er omkring 150 gange så radioaktivt som radium; mere aktivt end plutonium. På grund af den intense stråling "gløder" dette relativt bløde metal med et svagt, blåligt lys, som kan ses i "mørklagte" omgivelser. I kemisk henseende har actinium egenskaber der ligner lanthan.

Fase ved STP	Fast
Massefylde	10 g/cm3
Atommasse	227 u

Smeltepunkt	1500 K 1226.85 °C 2240.33 °F
Kogepunkt	3500 K 3226.85 °C 5840.33 °F
Fordampningsvarme	400 kJ/mol

Elektronegativitet (Pauling Scale)	1.1
Elektronaffinitet	33.77 kJ/mol
Oxidationstrin	+3 (a strongly basic oxide)
Ioniseringsenergier	499 kJ/mol 1170 kJ/mol 1900 kJ/mol 4700 kJ/mol

Elektronkonfiguration Kortfattet konfiguration	[Rn] 6d1 7s2
Elektronkonfiguration Fuld konfiguration	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 6d1 7s2
Elektronkonfigurationsdiagram	1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 6d1 7s2
Elektroner pr. Skal	2, 8, 18, 32, 18, 9, 2
Valenselektroner	2
Valency-elektroner	3
Bohrs atommodel	Figur: Skaldiagram af Actinium (Ac) atom.
Orbital diagram 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 6s 6p 6d 7s

Opdaget	Friedrich Oskar Giesel (1902)
Første isolation	Friedrich Oskar Giesel (1903)
Navngivet af	André-Louis Debierne (1899)
Opdagelse af actinium André-Louis Debierne, a French chemist, announced the discovery of a new element in 1899. He separated it from pitchblende residues left by Marie and Pierre Curie after they had extracted radium. In 1899, Debierne described the substance as similar to titanium and (in 1900) as similar to thorium. Friedrich Oskar Giesel found in 1902 a substance similar to lanthanum and called it "emanium" in 1904. After a comparison of the substances' half-lives determined by Debierne, Harriet Brooks in 1904, and Otto Hahn and Otto Sackur in 1905, Debierne's chosen name for the new element was retained because it had seniority, despite the contradicting chemical properties he claimed for the element at different times. Together with polonium, radium, and radon, actinium was one of the first non-primordial radioactive elements to be isolated. The name actinium originates from the Ancient Greek aktis, aktinos (ακτίς, ακτίνος), meaning beam or ray. Its symbol Ac is also used in abbreviations of other compounds that have nothing to do with actinium, such as acetyl, acetate and sometimes acetaldehyde.

CAS Number	7440-34-8
ChemSpider ID	22404
EC number	-
PubChem CID Number	23965