Curium

Curium is a silvery, hard radioactive metal named after Pierre and Marie Curie: the couple whose pioneering work on radioactivity opened up nuclear science. It produces enough heat from its radioactive decay to glow faintly red and is used to power nuclear batteries on spacecraft including the Mars rovers.

• Atomic Number9696 protons, 96 electrons
• Atomic Mass247.07035 u96× heavier than hydrogen
• State at Room TempSolidSolid
• Density13.51 g/cm³
• Melting / Boiling1344.8°C / 3126.8°C
• Discovered1944

What is Curium?

Curium has 96 protons. Cm-244 and Cm-242 have been used in Radioisotope Thermoelectric Generators (RTGs) for spacecraft. Cm-244 also serves as a target material to make heavier transuranic elements. Produced in 1944 by Seaborg, James, Morgan and Ghiorso at Berkeley.

Fact Curium is element 96, symbol Cm. As an actinide, it is part of the f-block of the periodic table: one of 15 radioactive elements from actinium (89) to lawrencium (103). All actinides are radioactive; none has a stable isotope. They are produced in nuclear reactors and by decay of heavier elements, and their chemistry has been studied using only microgram or nanogram quantities.

Where you find Curium

On Earth

Curium does not occur in significant natural abundance. It is produced only artificially, by bombarding heavier actinide targets with neutrons or lighter ions in nuclear reactors or particle accelerators. World production is measured in micrograms or milligrams per year.

How we use Curium

At element 96, practical applications are limited by the extreme difficulty of production and the intense radioactivity. Curium has 96 protons

How it was discovered

Curium has 96 protons. Cm-244 and Cm-242 have been used in Radioisotope Thermoelectric Generators (RTGs) for spacecraft. Cm-244 also serves as a target material to make heavier transuranic elements. Produced in 1944 by Seaborg, James, Morgan and Ghiorso at Berkeley.

Deeper dive: curium and the actinide series

The actinides (elements 89-103) form the lower of the two rows below the main body of the periodic table. They represent the filling of the 5f electron subshell. Unlike the lanthanides (the upper row), the actinides show greater variety in their chemistry because the 5f, 6d and 7s orbitals are close in energy. The early actinides, thorium through neptunium, can show many different oxidation states (e.g. uranium from +3 to +6). The heavier actinides increasingly resemble the lanthanides in preferring the +3 state.

All actinides beyond bismuth (83) are radioactive. The lightest, thorium, protactinium and uranium, have long enough half-lives to survive from the formation of the solar system. Neptunium and beyond are almost entirely synthetic, produced in nuclear reactors or accelerators. The transuranic elements were created at remarkable facilities including Oak Ridge National Laboratory, the Berkeley Cyclotron, the GSI in Darmstadt and JINR in Dubna.

Moving to 97 protons brings us to the next element on the periodic table.