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About Radium

Radium Bohr

Radium, as the story goes, was Marie and Pierre Curie’s greatest triumph and discovery while reducing uranium ore, or pitchblende, into its separate elements. Discovered mere months after polonium (1898) and from the same pitchblende sample, radium was first noted by the Curies due to its faint-blue luminescence under ambient conditions – a feature not common to other radioactive elements. Radium is 2.7 million times more radioactive than comparable amounts of uranium, and is so scarce that it takes the reduction of several tons of uranium ore to produce just a single gram of radium. Because of its high radioactivity and relative scarcity, radium is generally only made available in compounds, primarily radium chloride or radium bromide. Though credited with discovery in 1898, it wasn’t until Marie Curie performed electrolysis on radium chloride that radium was first successfully isolated in 1911. Radium was also the first element to be produced synthetically in the United States via deuteron bombardment of bismuth. Dr. John Jacob Livingood accomplished this feat in the radiation laboratory at the University of California, Berkeley in 1936.

Due to its luminescent properties, radium quickly became an element with industrial and commercial applications in the early 20th century. Its luminescence was placed on watch faces, aircraft instrumentation, nuclear panels, and the like. It was only after many of the human industrial applicators fell ill that radium paint was banned in the early 1960s,with cobalt, promethium, and tritium taking over its place in industry. Radium is a somewhat tragic historical footnote on scientific progress. With properties that fascinate humans on a fundamental level, radium was quickly touted as having curative powers. Radium was infused in many daily products such as toothpaste and spa water for these supposed powers, and was only banned when the link between radium and consumer products was identified as the root cause of otherwise healthy people falling ill. Radium was additionally used in a number of medical treatments in the 1920s-1930s that have since gone out of vogue. Today, only about 5 pounds of radium are produced each year, with most of the available material going towards medical research.

The Curie, now a standard unit of measure of radioactivity, is based on radium’s decay. This value is equal to the number of atoms that will decay in one second for a one-gram sample of 226Ra – about 37 billion decays per second. Radium decays into radon (also radioactive) and eventually lead. Four isotopes of radium occur in nature, with an additional 21 isotopes able to be generated synthetically. 226Ra is the most abundant isotope, with a half-life of roughly 1600 years, and is a naturally-occurring product of 238U decay. Other natural isotopes of radium are produced through uranium or thorium decay, and all natural occurrences of radium are found on Earth only in uranium ores.

Radium Properties

Radium Bohr ModelRadium is an S-Block, Group 2, Period 7 element. The number of electrons in each of Radium's shells is 2, 8, 18, 32, 18, 8, 2 and its electron configuration is [Rn] 7s2. The radium atom has a covalent radius of 221±2 pm and its Van der Waals radius is 283 pm. In its elemental form, CAS 7440-14-4, radium has a silvery white metallic appearance. Radium was discovered by Marie Skłodowska-Curie and her husband Pierre in 1898. In 1910, through the electrolysis of a pure radium chloride solution, radium was isolated as a pure metal by Marie Curie and André-Louis Debierne.

Radium information, including properties, research, applications and other useful facts are discussed below. Scientific facts such as the atomic structure, ionization energy, abundance on Earth, conductivity and thermal properties are included.

Symbol: Ra
Atomic Number: 88
Atomic Weight: 226
Element Category: alkaline earth metal
Group, Period, Block: 2, 7, s
Color: silvery white/ metallic
Other Names: Radio
Melting Point: 696 °C, 1284.8 °F,969.15 K
Boiling Point: 1737 °C, 3158.6 °F, 2010  K
Density: 5000 g/cm3
Liquid Density @ Melting Point: N/A
Density @ 20°C: 5.5 g/cm3
Density of Solid: N/A
Specific Heat: N/A
Superconductivity Temperature: N/A
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 7.15
Heat of Vaporization (kJ·mol-1): 136.7
Heat of Atomization (kJ·mol-1): 159
Thermal Conductivity: 18.6 W·m-1·K-1
Thermal Expansion: N/A
Electrical Resistivity: (20 °C) 1 µΩ·m
Tensile Strength: N/A
Molar Heat Capacity: N/A
Young's Modulus: N/A
Shear Modulus: N/A
Bulk Modulus: N/A
Poisson Ratio: N/A
Mohs Hardness: N/A
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: N/A
Pauling Electronegativity: 0.9
Sanderson Electronegativity: N/A
Allred Rochow Electronegativity: 0.97
Mulliken-Jaffe Electronegativity: 0.92 (sp orbital)
Allen Electronegativity: N/A
Pauling Electropositivity: 3.1
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 88
Protons: 88
Neutrons: 138
Electron Configuration: [Rn] 7s2
Atomic Radius: N/A
Atomic Radius, non-bonded (Å): 2.83
Covalent Radius: 221±2 pm
Covalent Radius (Å): 2.11
Van der Waals Radius: 283 pm
Oxidation States: 2 (strongly basic oxide)
Phase: Solid
Crystal Structure: body-centered cubic
Magnetic Ordering: nonmagnetic
Electron Affinity (kJ·mol-1) 9.649
1st Ionization Energy: 509.3 kJ·mol-1
2nd Ionization Energy: 979.0 kJ·mol-1
3rd Ionization Energy: N/A
CAS Number: 7440-14-4
EC Number: N/A
MDL Number: N/A
Beilstein Number: N/A
SMILES Identifier: [Ra]
InChI Identifier: InChI=1S/Ra
PubChem CID: 6328144
ChemSpider ID: 4886483
Earth - Total: 9.6 ppm
Mercury - Total: 7.4 ppm
Venus - Total: 10.1 ppm 
Earth - Seawater (Oceans), ppb by weight: 0.00000001
Earth - Seawater (Oceans), ppb by atoms: 3E-10
Earth -  Crust (Crustal Rocks), ppb by weight: 0.0001
Earth -  Crust (Crustal Rocks), ppb by atoms: 0.00001
Sun - Total, ppb by weight: N/A
Sun - Total, ppb by atoms: N/A
Stream, ppb by weight: 0.0000004
Stream, ppb by atoms: 0.000000002
Meterorite (Carbonaceous), ppb by weight: N/A
Meterorite (Carbonaceous), ppb by atoms: N/A
Typical Human Body, ppb by weight: 0.000001
Typical Human Body, ppb by atom: 0.00000003
Universe, ppb by weight: N/A
Universe, ppb by atom: N/A
Discovered By: Pierre Curie and Marie Curie
Discovery Date: 1898
First Isolation: Marie Curie (1902)

Radium Isotopes

Radium (Ra) has no stable or nearly stable isotopes.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
202Ra 202.00989(7) 2.6(21) ms [0.7(+33-3) ms] Unknown 0+ N/A 1533.16 -
203Ra 203.00927(9) 4(3) ms a to 199Rn; ß+ to 203Fr (3/2-) N/A 1541.24 -
204Ra 204.006500(17) 60(11) ms [59(+12-9) ms] a to 200Rn; ß+ to 204Fr 0+ N/A 1549.31 -
205Ra 205.00627(9) 220(40) ms [210(+60-40) ms] a to 201Rn; ß+ to 205Fr (3/2-) N/A 1557.39 -
206Ra 206.003827(19) 0.24(2) s a to 202Rn 0+ N/A 1565.47 -
207Ra 207.00380(6) 1.3(2) s a to 203Rn; ß+ to 207Fr (5/2-,3/2-) N/A 1573.55 -
208Ra 208.001840(17) 1.3(2) s a to 204Rn; ß+ to 208Fr 0+ N/A 1581.63 -
209Ra 209.00199(5) 4.6(2) s a to 205Rn; ß+ to 209Fr 5/2- N/A 1589.71 -
210Ra 210.000495(16) 3.7(2) s a to 206Rn; ß+ to 210Fr 0+ N/A 1597.79 -
211Ra 211.000898(28) 13(2) s a to 207Rn; ß+ to 211Fr 5/2(-) N/A 1605.87 -
212Ra 211.999794(12) 13.0(2) s a to 208Rn; ß+ to 212Fr 0+ N/A 1623.26 -
213Ra 213.000384(22) 2.74(6) min a to 209Rn; ß+ to 213Fr 1/2- N/A 1622.02 -
214Ra 214.000108(10) 2.46(3) s a to 210Rn; ß+ to 214Fr 0+ N/A 1630.1 -
215Ra 215.002720(8) 1.55(7) ms a to 211Rn (9/2+)# N/A 1638.18 -
216Ra 216.003533(9) 182(10) ns a to 212Rn; EC to 216Fr 0+ N/A 1646.26 -
217Ra 217.006320(9) 1.63(17) µs a to 213Rn (9/2+) N/A 1654.34 -
218Ra 218.007140(12) 25.2(3) µs a to 214Rn 0+ N/A 1662.42 -
219Ra 219.010085(9) 10(3) ms a to 215Rn (7/2)+ N/A 1661.18 -
220Ra 220.011028(10) 17.9(14) ms a to 216Rn 0+ N/A 1669.26 -
221Ra 221.013917(5) 28(2) s a to 217Rn; 14C 5/2+ N/A 1677.34 -
222Ra 222.015375(5) 38.0(5) s a to 218Rn; 14C 0+ N/A 1685.42 -
223Ra 223.0185022(27) 11.43(5) d a to 219Rn; 14C 3/2+ 0.271 1693.49 -
224Ra 224.0202118(24) 3.6319(23) d a to 220Rn; 12C 0+ N/A 1692.26 -
225Ra 225.023612(3) 14.9(2) d ß- to 225Ac 1/2+ -0.734 1700.33 -
226Ra 226.0254098(25) 1600(7) y a to 222Rn; 14C 0+ N/A 1708.41 -
227Ra 227.0291778(25) 42.2(5) min ß- to 227Ac 3/2+ -0.404 1716.49 -
228Ra 228.0310703(26) 5.75(3) y ß- to 228Ac 0+ N/A 1715.25 -
229Ra 229.034958(20) 4.0(2) min ß- to 229Ac 5/2(+) N/A 1723.33 -
230Ra 230.037056(13) 93(2) min ß- to 230Ac 0+ N/A 1731.41 -
231Ra 231.04122(32)# 103(3) s ß- to 231Ac (5/2+) N/A 1730.17 -
232Ra 232.04364(30)# 250(50) s ß- to 232Ac 0+ N/A 1738.25 -
233Ra 233.04806(50)# 30(5) s ß- to 233Ac 1/2+# N/A 1746.33 -
234Ra 234.05070(53)# 30(10) s ß- to 234Ac 0+ N/A 1745.09 -