Radium

Radium, ₈₈Ra

Radium electroplated on a very small sample of copper foil and covered with polyurethane to prevent reaction with the air
Radium
Pronunciation	/ˈreɪdiəm/ ​(RAY-dee-əm)
Appearance	silvery white metallic
Mass number	[226]
Radium 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 Ba ↑ Ra ↓ (Ubn) francium ← radium → actinium
Atomic number (Z)	88
Group	group 2 (alkaline earth metals)
Period	period 7
Block	s-block
Electron configuration	[Rn] 7s2
Electrons per shell	2, 8, 18, 32, 18, 8, 2
Physical properties
Phase at STP	solid
Melting point	973 K ​(700 °C, ​1292 °F) (disputed)
Boiling point	2010 K ​(1737 °C, ​3159 °F)
Density (near r.t.)	5.5 g/cm3
Heat of fusion	8.5 kJ/mol
Heat of vaporization	113 kJ/mol
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 819 906 1037 1209 1446 1799
Atomic properties
Oxidation states	common: +2
Electronegativity	Pauling scale: 0.9
Ionization energies	1st: 509.3 kJ/mol 2nd: 979.0 kJ/mol
Covalent radius	221±2 pm
Van der Waals radius	283 pm
Spectral lines of radium
Other properties
Natural occurrence	from decay
Crystal structure	​body-centered cubic (bcc) (cF4)
Lattice constant	a = 514.8 pm (near r.t.)[1]
Thermal conductivity	18.6 W/(m⋅K)
Electrical resistivity	1 µΩ⋅m (at 20 °C)
Magnetic ordering	nonmagnetic
CAS Number	7440-14-4
History
Discovery	Pierre and Marie Curie (1898)
First isolation	Marie Curie (1910)
Isotopes of radium v e
Main isotopes[2] Decay abun­dance half-life (t1/2) mode pro­duct 223Ra trace 11.43 d α 219Rn 224Ra trace 3.6319 d α 220Rn 225Ra trace 14.9 d β− 225Ac α[3] 221Rn Preview warning: Infobox Ra isotopes: Decay mode not recognised, input shown unedited "dm2=α" cat#D 226Ra trace 1599 y α 222Rn 228Ra trace 5.75 y β− 228Ac
Category: Radium view talk edit | references

Radium is a chemical element; it has symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather than oxygen) upon exposure to air, forming a black surface layer of radium nitride (Ra₃N₂). All isotopes of radium are radioactive, the most stable isotope being radium-226 with a half-life of 1,600 years. When radium decays, it emits ionizing radiation as a by-product, which can excite fluorescent chemicals and cause radioluminescence. For this property, it was widely used in self-luminous paints following its discovery. Of the radioactive elements that occur in quantity, radium is considered particularly toxic, and it is carcinogenic due to the radioactivity of both it and its immediate decay product radon as well as its tendency to accumulate in the bones.

Radium, in the form of radium chloride, was discovered by Marie and Pierre Curie in 1898 from ore mined at Jáchymov. They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1910, and soon afterwards the metal started being produced on larger scales in Austria, the United States, and Belgium. However, the amount of radium produced globally has always been small in comparison to other elements, and by the 2010s, annual production of radium, mainly via extraction from spent nuclear fuel, was less than 100 grams.

In nature, radium is found in uranium ores in quantities as small as a seventh of a gram per ton of uraninite, and in thorium ores in trace amounts. Radium is not necessary for living organisms, and its radioactivity and chemical reactivity make adverse health effects likely when it is incorporated into biochemical processes because of its chemical mimicry of calcium. As of 2018, other than in nuclear medicine, radium has no commercial applications. Formerly, from the 1910s to the 1970s, it was used as a radioactive source for radioluminescent devices and also in radioactive quackery for its supposed curative power. In nearly all of its applications, radium has been replaced with less dangerous radioisotopes, with one of its few remaining non-medical uses being the production of actinium in nuclear reactors.