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Actinium, 89Ac
Actinium
Pronunciation /ækˈtɪniəm/ (ak-TIN-ee-əm)
Appearance silvery-white
Mass number 227
Actinium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
La

Ac

(Uqu)
radiumactiniumthorium
Atomic number (Z) 89
Group group 3
Period period 7
Block   d
Electron configuration [Rn] 6d1 7s2
Electrons per shell 2, 8, 18, 32, 18, 9, 2
Physical properties
Phase at STP solid
Melting point (circa) 1323 K ​(1050 °C, ​1922 °F)
Boiling point 3471 K ​(3198 °C, ​5788 °F)
Density (near r.t.) 10 g/cm3
Heat of fusion 14 kJ/mol
Heat of vaporization 400 kJ/mol
Molar heat capacity 27.2 J/(mol·K)
Atomic properties
Oxidation states +2, +3 (a strongly basic oxide)
Electronegativity Pauling scale: 1.1
Covalent radius 215 pm
Color lines in a spectral range
Spectral lines of actinium
Other properties
Natural occurrence from decay
Crystal structure face-centered cubic (fcc)
Face-centered cubic crystal structure for actinium
Thermal conductivity 12 W/(m⋅K)
Magnetic ordering no data
CAS Number 7440-34-8
History
Discovery André-Louis Debierne (1899)
First isolation André-Louis Debierne (1899)
Main isotopes of actinium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
225Ac trace 10 d α 5.935 221Fr
226Ac syn 29.37 h β 1.117 226Th
ε 0.640 226Ra
α 5.536 222Fr
227Ac trace 21.772 y β 0.045 227Th
α 5.042 223Fr

Actinium is chemical element 89 on the periodic table. Its symbol is Ac. Actinium's mass is 227 g/mol.

Actinium is a silver radioactive, solid metal in actinide group. It is so radioactive that it glows in the dark. Even a small amount of actinium is dangerous to people.

History

Actinium was discovered in 1899 by André-Louis Debierne, a French chemist. In 1899, Debierne described the substance as similar to titanium and (in 1900) as similar to thorium.

Properties

Actinium is a soft, silvery-white, radioactive metal.

Because its strong radioactivity, actinium glows in the dark with a pale blue light.

Actinium reacts quickly with oxygen and moisture in air forming a white coating (actinium oxide) that stops the actinium from oxidizing.

Occurence

Actinium is only found in very tiny amounts in uranium and thorium ores.

Uses

Actinium is now being studied for use in cancer treatments. It can be used in radiation therapy.

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See also

Kids robot.svg In Spanish: Actinio para niños

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