Curium is a radioactive chemical element with the symbol Cm and atomic number 96 in the periodic table of elements. This rare-earth element is not found in Earth’s crust due to the fact that it’s a man-made substance. As a member of the family of transuranic elements, this actinide has three and occasionally four valence electrons, which makes curium highly unstable in reactions with other chemical elements.
Chemical and Physical Properties of Curium
| Property | Value |
| The symbol in the periodic table of elements | Cm |
| Atomic number | 96 |
| Atomic weight (mass) | (247) g.mol -1 |
| Group number | N/A (Actinides) |
| Period | 7 |
| Color | Silvery |
| Physical state | Solid metal |
| Half-life | 163 days |
| Electronegativity according to Pauling | χ = 1.3 |
| Density | 13.51 g.cm-3 at 20°C |
| Melting point | 1340 °C |
| Boiling point | Unknown |
| Van der Waals radius | Unknown |
| Ionic radius | Unknown |
| Isotopes | No stable isotopes / 19 radioisotopes |
| Most characteristic isotope | Curium-247 |
| Electronic shell | [Rn] 5f7 6d1 7s2 |
| The energy of the first ionization | Unknown |
| The energy of the second ionization | Unknown |
| Discovery date | In 1944 by Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso |
Despite being discovered before americium, curium follows the aforementioned chemical element in the periodic table. With the symbol Cm, atomic number 96, atomic mass of (247) g.mol -1, and electron configuration [Rn] 5f7 6d1 7s2, curium is a hard and brittle metal with a density of 13.51 g.cm-3 at 20°C. It tarnishes at room temperature when exposed to dry air.
The atomic radius and the boiling point of this insoluble member of the actinides are unknown. Regarding the melting point, it’s achieved at 1340 °C, which is higher than the transuranic elements neptunium (637 °C), plutonium (639 °C), and americium (1173 °C) that come before curium in the periodic table.
Curium reacts mostly with oxygen and assumes a +3 oxidation state as its most stable result of the reaction with oxygen. Due to the high spontaneous fission rate of this radioactive substance, it acts as a strong source of radiation. The analysis of the crystal structure of curium shows resemblance to the crystals of the other actinides: americium, berkelium, and californium.
How Was Curium Discovered?
In 1944, a group of scientists working at the University of California, Berkeley, attempted to secretly synthesize a new radioactive element. One day in July, the American chemists Glenn Seaborg, Ralph A. James, and Albert Ghiorso, conducted an experiment at a wartime Metallurgical Laboratory at the University of Chicago, U.S.
The group of scientists bombarded plutonium Pu-239 with helium-ion alpha particles in a 60-inch cyclotron. This strictly confidential chemical trial resulted in the discovery of a new radioactive chemical element in its pure elemental form – curium-242 and one free neutron.
However, this great discovery wasn’t announced immediately as World War II was still raging. After the war, the new chemical element was introduced to the world in November 1947. The same year, the American nuclear chemists Louis Werner and Isadore Perlman attempted to bombard americium-241 with neutrons in order to produce more significant quantities of this radioactive actinide.
The metallic form of this man-made chemical element was obtained in 1951 by W. W. T. Crane, J. C. Wallmann. and B. B. Cunningham.
How Did Curium Get Its Name?
This radioactive chemical element was named in honor of Marie and Pierre Curie, both recognized as pioneers of radioactivity.
Where Can You Find Curium?
Apart from being produced in laboratories by neutron capture reactions of plutonium and americium isotopes, curium can be found in the used nuclear fuel of nuclear power plants, as well as in locations where nuclear testings are conducted.
Curium in Everyday Life
This radioactive and insufficiently studied chemical element doesn’t have wide use in everyday life. However, there are many significant applications of curium in space technologies, power generation industries, radiology, and scientific researches:
- Curium-244 and curium-242 isotopes are used as a fuel in nuclear reactors and thermo-electric and thermionic converters manufactured by the power generation industries.
- Curium isotopes are deployed as alpha emitters for alpha particle X-ray spectrometry;
- In medicine, curium isotopes are used as power sources in artificial pacemakers production;
- Regarding the medical application of curium, this chemical is also used for the production of Pu-238 which is one of the main components of the artificial pacemakers;
- Its application in scientific research as one of the main constituents of the X-ray spectrometer used for quantitative analysis is of high importance.
How Dangerous Is Curium?
Curium is a radioactive metal that imposes a great hazard upon human health and the environment. According to the United States National Institute of Standards and Technology, curium may lead to adverse health effects if inhaled, ingested, or if it comes into skin contact. Upon exposure to any levels of this substance, it can cause severe skin burns, or eye damage resulting in blindness.
Since curium shares the properties of all other radioactive chemical elements, this substance also imposes a great risk of cancer upon any type of exposure to its toxicity. By accumulation in the lungs, bones, and liver, curium triggers the destruction of the red blood cells’ mechanism which leads to various forms of cancer.
Environmental Effects of Curium
Apart from being a health hazard, this highly radioactive metal also presents a significant biological hazard. This holds true especially when it comes to radioactive material spills from nuclear plants. The radiation brought about by the improper handling of nuclear waste and the insolubility of curium negatively impact both the environment and the life in it.
Isotopes of Curium
Owed to the high radioactivity of this element, there are no stable isotopes among the 19 radioisotopes and 7 nuclear isomers of curium. With a half-life of about 15,600,000 years, 257curium is the most stable isotope of curium that undergoes alpha decay to 243plutonium isotope.
| Nuclide[n 1] | Z | N | Isotopic mass (Da)[n 2][n 3] | Half-life[n 4] | Decaymode[n 5] | Daughterisotope | Spin andparity[n 6][n 4] |
| Excitation energy[n 4] | |||||||
| 233Cm | 96 | 137 | 233.05077(8) | 27(10) s | β+ (80%) | 233Am | 3/2+# |
| α (20%) | 229Pu | ||||||
| 234Cm | 96 | 138 | 234.05016(2) | 52(9) s | β+ (71%) | 234Am | 0+ |
| α (27%) | 230Pu | ||||||
| SF (2%) | (various) | ||||||
| 235Cm | 96 | 139 | 235.05143(22)# | 5# min | β+ | 235Am | 5/2+# |
| α | 231Pu | ||||||
| 236Cm | 96 | 140 | 236.05141(22)# | 6.8(0.8) min | β+ (82%) | 236Am | 0+ |
| α (18%) | 232Pu | ||||||
| 237Cm | 96 | 141 | 237.05290(22)# | 20# min | β+ | 237Am | 5/2+# |
| α | 233Pu | ||||||
| 238Cm | 96 | 142 | 238.05303(4) | 2.4(1) h | EC (90%) | 238Am | 0+ |
| α (10%) | 234Pu | ||||||
| 239Cm | 96 | 143 | 239.05496(11)# | 2.5(0.4) h | β+ (99.9%) | 239Am | (7/2−) |
| α (.1%) | 235Pu | ||||||
| 240Cm | 96 | 144 | 240.0555295(25) | 27(1) d | α (99.5%) | 236Pu | 0+ |
| EC (.5%) | 240Am | ||||||
| SF (3.9×10−6%) | (various) | ||||||
| 241Cm | 96 | 145 | 241.0576530(23) | 32.8(2) d | EC (99%) | 241Am | 1/2+ |
| α (1%) | 237Pu | ||||||
| 242Cm[n 7] | 96 | 146 | 242.0588358(20) | 162.8(2) d | α | 238Pu | 0+ |
| SF (6.33×10−6%) | (various) | ||||||
| CD (10−14%)[n 8] | 208Pb34Si | ||||||
| β+β+ (rare) | 242Pu | ||||||
| 242mCm | 2800(100) keV | 180(70) ns | |||||
| 243Cm | 96 | 147 | 243.0613891(22) | 29.1(1) y | α (99.71%) | 239Pu | 5/2+ |
| EC (.29%) | 243Am | ||||||
| SF (5.3×10−9%) | (various) | ||||||
| 243mCm | 87.4(1) keV | 1.08(3) µs | IT | 243Cm | 1/2+ | ||
| 244Cm[n 7] | 96 | 148 | 244.0627526(20) | 18.10(2) y | α | 240Pu | 0+ |
| SF (1.34×10−4%) | (various) | ||||||
| 244m1Cm | 1040.188(12) keV | 34(2) ms | IT | 244Cm | 6+ | ||
| 244m2Cm | 1100(900)# keV | >500 ns | SF | (various) | |||
| 245Cm | 96 | 149 | 245.0654912(22) | 8.5(1)×103 y | α | 241Pu | 7/2+ |
| SF (6.1×10−7%) | (various) | ||||||
| 245mCm | 355.92(10) keV | 290(20) ns | IT | 245Cm | 1/2+ | ||
| 246Cm | 96 | 150 | 246.0672237(22) | 4.76(4)×103 y | α (99.97%) | 242Pu | 0+ |
| SF (.0261%) | (various) | ||||||
| 246mCm | 1179.66(13) keV | 1.12(0.24) s | IT | 246Cm | 8- | ||
| 247Cm | 96 | 151 | 247.070354(5) | 1.56(5)×107 y | α | 243Pu | 9/2− |
| 247m1Cm | 227.38(19) keV | 26.3(0.3) µs | IT | 247Cm | 5/2+ | ||
| 247m2Cm | 404.90(3) keV | 100.6(0.6) ns | IT | 247Cm | 1/2+ | ||
| 248Cm | 96 | 152 | 248.072349(5) | 3.48(6)×105 y | α (91.74%) | 244Pu | 0+ |
| SF (8.26%) | (various) | ||||||
| β−β− (rare) | 248Cf | ||||||
| 248mCm | 1458.1(1) keV | 146(18) µs | IT | 248Cm | (8-) | ||
| 249Cm | 96 | 153 | 249.075953(5) | 64.15(3) min | β− | 249Bk | 1/2(+) |
| 249mCm | 48.758(17) keV | 23 µs | α | 245Pu | (7/2+) | ||
| 250Cm | 96 | 154 | 250.078357(12) | 8300# y | SF (74%)[n 9] | (various) | 0+ |
| α (18%) | 246Pu | ||||||
| β− (8%) | 250Bk | ||||||
| 251Cm | 96 | 155 | 251.082285(24) | 16.8(2) min | β− | 251Bk | (1/2+) |
List of Curium Compounds
The compounds of curium comprise a list of numerous oxides, halides, chalcogenides, and pnictides:
- Curium trifluoride CmF3
- Curium tetrafluoride CmF4
- Curium trichloride CmCl3
- Curium triiodide CmI3
- Curium oxide CmO
- Curium dioxide CmO2
- Dicurium trioxide Cm2O3
- Curium hydroxide Cm(OH)3
5 Interesting Facts and Explanations
- Curium is the third transuranium element that was discovered and synthesized in a chemical laboratory;
- The milligram amounts of curium produced in the laboratory were so nanoscopic in size that this element could be detected only by its radioactive property.
- A gram of curium is capable of producing 3 watts of thermal energy.
- This radioactive metal imposes an inconsequential fire and explosion hazard.
- The half-life of 247curium isotope is 647 times longer than the half-life of 239plutonium isotope.