Curium connects synthetic-element research to planetary exploration. Curium-244 sources in Mars-rover instruments help excite characteristic X-rays from rocks and soils. Measuring those X-rays reveals elemental composition, showing how radiation from one element can become a tool for investigating many others.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
Why does a curium-powered instrument not imply curium in a Martian rock?
Curium-244 source in an alpha-particle X-ray spectrometer
FOLLOW THIS RELATIONSHIP
Separate source and specimen
The APXS instrument carries a curium radiation source while the Martian rock is the specimen. Keep those material identities separate before interpreting any detected signal.
Explore the model (optional)
CmFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
Optional: check your understanding
USE THE EXPLANATION
Where does the curium belong in this account?
Atomic identity, reference properties and structure models
INTERACTIVE 3D96 visible sites
An electron censusDrag to rotate · scroll or pinch to zoom
[Rn] 5f7 6d1 7s2. Grouping electrons by principal shell connects the neutral-atom configuration to periodic-table patterns.
What this representation means
A three-dimensional counting diagram. Dots are count markers, not measured electron positions; spherical placement and spacing are arbitrary. There are no electron trajectories here. Orbitals describe quantum states.
Curium was discovered in 1944 by Glenn Seaborg, Ralph James and Albert Ghiorso, during the same broad program that established several transuranium elements. It was named for Marie and Pierre Curie, whose discoveries had helped launch research. Public announcement followed in 1945. Curium’s history links laboratory-made atoms with an older scientific tradition of identifying elements from the radiation and chemistry of extremely small samples.
1944
Discovery
The team identifies curium in artificially produced material.
1945
Public announcement
Curium is publicly announced after its wartime discovery.
Curium used in research is produced through nuclear reactions rather than recovered from a natural deposit. Its form part of the material flows of specialized reactors and actinide laboratories. Different isotopes support different purposes, so a description of curium as simply radioactive leaves out information essential to understanding its use.
Curium commonly forms +3 . Its electronic structure makes it a useful point of comparison across the actinide series, while isotope-dependent supplies the radiation used in certain instruments. A curium-containing source is therefore simultaneously a chemical material and a collection of unstable , with each description answering different questions.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
CITE THIS PAGE
Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
solid
293.15 K, 101.325 kPa
Melting point in K
1613 K
at standard pressure unless noted
Boiling point in K
3383 K
101.325 kPa
Density in g/cm³
13.51 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity in Pauling
1.28 Pauling
Pauling scale
First ionization energy in kJ/mol
581 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
169 pm
single-bond covalent radius
Common oxidation states
+3
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust
Not recorded
upper continental crust, mass fraction
Has stable isotopes
Noderived
Discovery year in CE
1944 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 7
Cm 1.28 Pauling · Curium
Electronegativity across period 7. Exact values.
Ra
0.9
Ac
1.1
Th
1.3
Pa
1.5
U
1.38
Np
1.36
Pu
1.28
Am
1.13
Cm
1.28
Bk
1.3
Cf
1.3
Es
1.3
Fm
1.3
Md
1.3
No
1.3
Lr
1.3
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
