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About Curium

Curium Bohr

Curium, a radioactive transuranic chemical element, was first synthesized in 1944 by Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso at the University of California at Berkeley. The work was related to the Manhattan Project, so the discovery was kept classified until the end of World War II. The announcement was planned at an American Chemical Society meeting, but Seaborg let the news slip a few days early on a kids’ radio show when a precocious young guest asked if he had discovered any new transuranic elements lately. The name was selected in honor of Marie Sklodowska-Curie and Pierre Curie and their pioneering research in radioactivity.

Curium is used as a fuel in radioisotope thermoelectric generators (RTGs), and as an alpha particle source in alpha particle X-ray spectrometers (APXS). AXPS instruments are primarily used in space exploration missions, and have been included in a number of Mars rovers. Curium is also used in the production of higher transuranic and transactinide elements.

Curium does not occur naturally on Earth and is typically produced by bombarding uranium or plutonium with neutrons in nuclear reactors. The pure element is hard, brittle, malleable, and appears a lustrous silvery white.

Curium Properties

Curium Bohr ModelCurium is a Block P, Group 3, Period 7 element. The number of electrons in each of curium's shells is 2, 8, 18, 32, 25, 9, 2 and its electron configuration is [Rn] 5f7 6d1 7s2. The curium atom has a radius of 174pm. In its elemental form, curium's CAS number is 7440-51-9. Curium is radioactive. It is produced by bombarding uranium or plutonium with neutrons in nuclear reactors. Curium is found in spent nuclear fuel and small amounts are produced for research. Curium was discovered by Glenn T. Seaborg, Ralph A. James and Albert Ghiorso at the University of California, Berkeley in 1944. The element was named in honor of Marie and Pierre Curie.

Curium information, including technical data, properties, 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: Cm
Atomic Number: 96
Atomic Weight: 247
Element Category: Actinide
Group, Period, Block: n/a, 7, f
Color: silvery-white
Other Names: Curio
Melting Point: 1345 °C, 2453 °F, 1618 K
Boiling Point: 3110 °C, 5630 °F, 3383 K
Density: 13300 kg·m3
Liquid Density @ Melting Point: N/A
Density @ 20°C: 13.5 g/cm3
Density of Solid: 13510 kg·m3
Specific Heat: N/A
Superconductivity Temperature: N/A
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 15
Heat of Vaporization (kJ·mol-1): about 32
Heat of Atomization (kJ·mol-1): 382
Thermal Conductivity: N/A
Thermal Expansion: N/A
Electrical Resistivity: 1.25 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: 1.3
Sanderson Electronegativity: N/A
Allred Rochow Electronegativity: 1.2
Mulliken-Jaffe Electronegativity: N/A
Allen Electronegativity: N/A
Pauling Electropositivity: 2.7
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 96
Protons: 96
Neutrons: 151
Electron Configuration: [Rn] 5f7 6d1 7s2
Atomic Radius: 174 pm
Atomic Radius,
non-bonded (Å):
Covalent Radius: 169±3 pm
Covalent Radius (Å): 1.68
Van der Waals Radius: N/A
Oxidation States: 4, 3 (amphoteric oxide)
Phase: Solid
Crystal Structure: hexagonal close-packed
Magnetic Ordering: antiferromagnetic (paramagnetic transition at 52 K)
Electron Affinity (kJ·mol-1) Unknown
1st Ionization Energy: 581 kJ·mol-1 (estimated)
2nd Ionization Energy: N/A
3rd Ionization Energy: N/A
CAS Number: 7440-51-9
EC Number: N/A
MDL Number: N/A
Beilstein Number: N/A
SMILES Identifier: [Cm]
InChI Identifier: InChI=1S/Cm
PubChem CID: 23979
ChemSpider ID: 22415
Earth - Total: N/A
Mercury - Total: N/A
Venus - Total: N/A
Earth - Seawater (Oceans), ppb by weight: N/A
Earth - Seawater (Oceans), ppb by atoms: N/A
Earth -  Crust (Crustal Rocks), ppb by weight: N/A
Earth -  Crust (Crustal Rocks), ppb by atoms: N/A
Sun - Total, ppb by weight: N/A
Sun - Total, ppb by atoms: N/A
Stream, ppb by weight: N/A
Stream, ppb by atoms: N/A
Meterorite (Carbonaceous), ppb by weight: N/A
Meterorite (Carbonaceous), ppb by atoms: N/A
Typical Human Body, ppb by weight: N/A
Typical Human Body, ppb by atom: N/A
Universe, ppb by weight: N/A
Universe, ppb by atom: N/A
Discovered By: Glenn Seaborg, Ralph James, Albert Ghiorso
Discovery Date: 1944
First Isolation: Carl Gustaf Mosander (1842)

Curium Isotopes

Curium is an artificial element. It has no stable isotopes.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
232Cm 232 1? min N/A 0+ N/A N/A -
233Cm 233.05077(8) 1# min ß+ to 233Am; a to 229Pu 3/2+# N/A 1758.192017 -
234Cm 234.05016(2) 51(12) s ß+ to 234Am; a to 230Pu 0+ N/A 1766.785034 -
235Cm 235.05143(22)# 5# min ß+ to 235Am; a to 231Pu 5/2+# N/A 1773.598022 -
236Cm 236.05141(22)# 10# min ß+ to 236Am; a to 232Pu 0+ N/A 1781.843018 -
237Cm 237.05290(22)# 20# min ß+ to 237Am; a to 233Pu 5/2+# N/A 1788.530029 -
238Cm 238.05303(4) 2.4(1) h EC to 238Am; a to 234Pu 0+ N/A 1796.484497 -
239Cm 239.05496(11)# ~2.9 h ß+ to 239Am; a to 235Pu (7/2-) N/A 1802.754028 -
240Cm 240.0555295(25) 27(1) d a to 236Pu; EC to 240Am; SF 0+ N/A 1810.295898 -
241Cm 241.0576530(23) 32.8(2) d a to 237Pu; EC to 241Am 1/2+ N/A 1816.385254 -
242Cm 242.0588358(20) 162.8(2) d a to 238Pu; SF 0+ N/A 1823.35498 -
243Cm 243.0613891(22) 29.1(1) y a to 239Pu; EC to 243Am 5/2+ 0.41 1829.04834 -
244Cm 244.0627526(20) 18.10(2) y a to 240Pu; SF 0+ N/A 1835.848999 -
245Cm 245.0654912(22) 8.5(1)×103 y a to 241Pu; SF 7/2+ 0.5 1841.368774 -
246Cm 246.0672237(22) 4.76(4)×103 y a to 242Pu; SF 0+ N/A 1847.826782 -
247Cm 247.070354(5) 1.56(5)×107 y a to 243Pu 9/2- 0.37 1852.983154 -
248Cm 248.072349(5) 3.48(6)×105 y a to 244Pu; SF 0+ N/A 1859.195801 -
249Cm 249.075953(5) 64.15(3) min ß- to 249Bk 1/2(+) N/A 1863.90918 -
250Cm 250.078357(12) 8300# y a to 246Pu; ß- to 250Bk; SF 0+ N/A 1869.741577 -
251Cm 251.082285(24) 16.8(2) min ß- to 251Bk (1/2+) N/A 1874.154785 -
252Cm 252.08487(32)# <1 d ß- to 252Bk 0+ N/A 1879.812012 -