Californium (Cf)

Silvery-gray metal

Californium is a powerful neutron source used to detect gold ore and start nuclear reactors, and with [Rn] 5f¹⁰ 7s², californium-252 (half-life 2.645 years) undergoes spontaneous fission, emitting 2.31×10⁶ neutrons per second per microgram. It is used in neutron radiography, cancer therapy, and reactor startup sources.

Key metrics

Density15.1g/cm³

Melting point1,173K

Boiling point1,743K

Electronegativity1.3Pauling

Discovery

1950discovered

Discovered by: Lawrence Berkeley Lab
Reactivity profile: Intensely radioactive
Reactivity: Medium
Bonding: Metallic

Electron configuration

\textcolor{#6b7280}{[Rn]}\; \textcolor{#a855f7}{5_{f}^{10}}\; \textcolor{#ef4444}{7_{s}^{2}}

[Rn] 5f10 7s2

Wave function

\Psi_{\text{Cf}} \approx \frac{1}{\sqrt{98!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{98}(\mathbf{r}_{98}) \right|

Probability density $|\Psi|^2$ across the Cf valence shell.

Crystal structure

Double Hexagonal Close-Packed

Lattice constantsa 1.00 · b 1.00 · c 2.00

Cell anglesα 90° · β 90° · γ 120°

Coordination number12

Atoms per cell4

Atomic packing factor0.74

Physical properties

Atomic radius: 186 pm
Ionization energy: 608 kJ/mol
Electron affinity: 0 kJ/mol
Crystal structure: Double hexagonal close-packed

Oxidation states

+2+3+4

Acid/base

Basic

Strongly acidicStrongly basic

State at 25 °CSolid

1173 K1743 K298 K

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

432.0nmCf I (blue)Violet60%

490.0nmCf ICyan40%

505.0nmCf I (green)Cyan100%

Dominant line 505.0 nmRange 432–505 nmTransitions 3