This article is about the chemical element. For other uses, see Radium (disambiguation).
Not to be confused with Radon.
Chemical element, symbol Ra and atomic number 88
Radium, 88Ra
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
+2 (expected to have a strongly basic oxide)
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
226Ra
trace
1599 y
α
222Rn
228Ra
trace
5.75 y
β−
228Ac
Category: Radium
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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.
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 1911.[3]
In nature, radium is found in uranium ores and (to a lesser extent) thorium ores in trace amounts as small as a seventh of a gram per ton of uraninite. 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 2014[update], other than its use 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. These applications have become obsolete owing to radium's toxicity; as of 2020[update], less dangerous isotopes (of other elements) are instead used in radioluminescent devices.
^Arblaster, John W. (2018). Selected Values of the Crystallographic Properties of Elements. Materials Park, Ohio: ASM International. ISBN 978-1-62708-155-9.
^Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF). Chinese Physics C. 45 (3): 030001. doi:10.1088/1674-1137/abddae.
^"Radium". Elements / Periodic Table. rsc.org. Royal Society of Chemistry. Archived from the original on 24 March 2016. Retrieved 5 July 2016.
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