![]() | ||||||||||||||||||||||||||||||||||||
Radium | ||||||||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Pronunciation | /ˈreɪdiəm/ | |||||||||||||||||||||||||||||||||||
Appearance | silvery white metallic | |||||||||||||||||||||||||||||||||||
Mass number | [226] | |||||||||||||||||||||||||||||||||||
Radium in the periodic table | ||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||
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
| ||||||||||||||||||||||||||||||||||||
Atomic properties | ||||||||||||||||||||||||||||||||||||
Oxidation states | +2 (expected to have a strongly basic oxide) | |||||||||||||||||||||||||||||||||||
Electronegativity | Pauling scale: 0.9 | |||||||||||||||||||||||||||||||||||
Ionization energies |
| |||||||||||||||||||||||||||||||||||
Covalent radius | 221±2 pm | |||||||||||||||||||||||||||||||||||
Van der Waals radius | 283 pm | |||||||||||||||||||||||||||||||||||
![]() | ||||||||||||||||||||||||||||||||||||
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 | ||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||
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. Of the radioactive elements that occur in quantity, radium is considered the most toxic.
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.
© MMXXIII Rich X Search. We shall prevail. All rights reserved. Rich X Search