#96 / 118
96Cm[247]
Actinidessolid at STPF-block

Curium

Group: f-block•Period: 7•Standard Atomic Weight: [247] u
Open Full Periodic TableView Bohr Model

Why is Curium in this position?

Understanding the scientific rationale behind Curium's position in the periodic table:

Group Assignment
Group Lanthanide / Actinide

Actinide series element filling the 5f subshell.

Period Assignment
Period 7

Belongs to Period 7 because its outermost electrons occupy n=7.

Orbital Block
F-block

Belongs to the f-block actinide series maintaining half-filled 5f⁷ orbital stability.

Chemical Category
Actinides

Classified as an actinide radioactive synthetic metal.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 18, 32, 25, 9, 2]

Bohr Atomic Shell Model(2, 8, 18, 32, 25, 9, 2)

Hover or tap any shell orbit ring to inspect electron counts and 2n² capacities.

96 Protons (p⁺)151 Neutrons (n⁰)
KShell K: Electron 1 of 2Shell K: Electron 2 of 2LShell L: Electron 1 of 8Shell L: Electron 2 of 8Shell L: Electron 3 of 8Shell L: Electron 4 of 8Shell L: Electron 5 of 8Shell L: Electron 6 of 8Shell L: Electron 7 of 8Shell L: Electron 8 of 8MShell M: Electron 1 of 18Shell M: Electron 2 of 18Shell M: Electron 3 of 18Shell M: Electron 4 of 18Shell M: Electron 5 of 18Shell M: Electron 6 of 18Shell M: Electron 7 of 18Shell M: Electron 8 of 18Shell M: Electron 9 of 18Shell M: Electron 10 of 18Shell M: Electron 11 of 18Shell M: Electron 12 of 18Shell M: Electron 13 of 18Shell M: Electron 14 of 18Shell M: Electron 15 of 18Shell M: Electron 16 of 18Shell M: Electron 17 of 18Shell M: Electron 18 of 18NShell N: Electron 1 of 32Shell N: Electron 2 of 32Shell N: Electron 3 of 32Shell N: Electron 4 of 32Shell N: Electron 5 of 32Shell N: Electron 6 of 32Shell N: Electron 7 of 32Shell N: Electron 8 of 32Shell N: Electron 9 of 32Shell N: Electron 10 of 32Shell N: Electron 11 of 32Shell N: Electron 12 of 32Shell N: Electron 13 of 32Shell N: Electron 14 of 32Shell N: Electron 15 of 32Shell N: Electron 16 of 32Shell N: Electron 17 of 32Shell N: Electron 18 of 32Shell N: Electron 19 of 32Shell N: Electron 20 of 32Shell N: Electron 21 of 32Shell N: Electron 22 of 32Shell N: Electron 23 of 32Shell N: Electron 24 of 32Shell N: Electron 25 of 32Shell N: Electron 26 of 32Shell N: Electron 27 of 32Shell N: Electron 28 of 32Shell N: Electron 29 of 32Shell N: Electron 30 of 32Shell N: Electron 31 of 32Shell N: Electron 32 of 32OShell O: Electron 1 of 25Shell O: Electron 2 of 25Shell O: Electron 3 of 25Shell O: Electron 4 of 25Shell O: Electron 5 of 25Shell O: Electron 6 of 25Shell O: Electron 7 of 25Shell O: Electron 8 of 25Shell O: Electron 9 of 25Shell O: Electron 10 of 25Shell O: Electron 11 of 25Shell O: Electron 12 of 25Shell O: Electron 13 of 25Shell O: Electron 14 of 25Shell O: Electron 15 of 25Shell O: Electron 16 of 25Shell O: Electron 17 of 25Shell O: Electron 18 of 25Shell O: Electron 19 of 25Shell O: Electron 20 of 25Shell O: Electron 21 of 25Shell O: Electron 22 of 25Shell O: Electron 23 of 25Shell O: Electron 24 of 25Shell O: Electron 25 of 25PShell P: Electron 1 of 9Shell P: Electron 2 of 9Shell P: Electron 3 of 9Shell P: Electron 4 of 9Shell P: Electron 5 of 9Shell P: Electron 6 of 9Shell P: Electron 7 of 9Shell P: Electron 8 of 9Shell P: Electron 9 of 9QShell Q: Electron 1 of 2Shell Q: Electron 2 of 2CmZ = 96

Educational Note: This Niels Bohr planetary model visually illustrates principal quantum energy shells ($n=1, 2, 3\dots$) and electron counts. In modern quantum mechanics (Schrödinger model), electrons do not orbit in fixed circular planetary tracks, but exist as 3D probability clouds (orbitals: $s, p, d, f$) governed by the Heisenberg uncertainty principle.

Electron Shell Filling Breakdown

Shell K (n=1):2 / 2 electrons (100%)
Shell L (n=2):8 / 8 electrons (100%)
Shell M (n=3):18 / 18 electrons (100%)
Shell N (n=4):32 / 32 electrons (100%)
Shell O (n=5):25 / 50 electrons (50%)
Shell P (n=6):9 / 72 electrons (13%)
Shell Q (n=7):2 / 98 electrons (2%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f⁷ 6s² 6p⁶ 6d¹ 7s²

Neutral ground state configuration. Valence electrons: 10.

Atomic & Quantum Properties

Electronegativity (Pauling)1.3 Pauling
1st Ionization Energy581 kJ/mol
Electron Affinity-47 kJ/mol
Atomic Radius (empirical)169 pm
Common Oxidation States+3
Crystal StructureDouble HCP

Physical & Thermal Properties

Density at STP13.51 g/cm³
Melting Point1345 °C (1618 K)
Boiling Point3110 °C (3383 K)
Magnetic OrderingParamagnetic
Discovery Year1944
Discovered ByGlenn T. Seaborg, Ralph A. James & Albert Ghiorso

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Alpha Particle X-ray Spectrometer (APXS) scientific alpha source on NASA Mars Exploration Rovers (Curiosity, Opportunity)
  • Heavy radioisotope thermoelectric generators (Curium-244 generates 2.8 watts of thermal heat per gram)
  • Target material for synthesizing heavier transuranic and superheavy elements (Californium, Oganesson)
Occurrence in Nature

Synthesized artificially in high-flux nuclear reactors by multi-neutron bombardment of plutonium or americium.

Etymology & Name Origin

Named in honor of Marie and Pierre Curie, pioneers of radioactivity

Important Chemical Compounds
Cm₂O₃ (Curium(III) oxide)
CmO₂ (Curium(IV) oxide)
CmF₄ (Curium tetrafluoride)
Interesting Chemical Facts
  • • Curium glows with a mesmerizing purple luminescence in the dark as its relentless alpha radiation ionizes nitrogen in surrounding air.
  • • The Curiosity Mars rover analyzed rocks on Gale Crater using an APXS instrument containing a radioactive curium-244 sensor.
  • • Like its lanthanide counterpart gadolinium, curium has a stable half-filled 5f⁷ electron shell ([Rn] 5f⁷ 6d¹ 7s²).
Safety & Handling Note

Dangerous alpha-emitting bone seeker; generates intense self-heating and radiolytic decay heat.

Explore Neighborhood Elements

Same Period (Period 7):
#87Fr#88Ra#89Ac#90Th#91Pa#92U#93Np#94Pu#95Am#97Bk#98Cf#99Es#100Fm#101Md#102No#103Lr#104Rf#105Db#106Sg#107Bh#108Hs#109Mt#110Ds#111Rg#112Cn#113Nh#114Fl#115Mc#116Lv#117Ts#118Og