Atomic number 98
Californium
Actinide
No photo: here’s why
Californium is among the most expensive substances on Earth, made in microscopic specks. A glimpse or two has been recorded - but you will never encounter it.
Quick facts
- Atomic mass
- 251.00
- Group
- –
- Period
- 7
- State (STP)
- solid
- Electronegativity
- 1.30
- Common ox. states
- +2, +3, +4
Properties
[Rn] 5f¹⁰ 7s²
- Ionization energy
- 608.0 kJ/mol
- Electron affinity
- –
- Melting point
- 1173.00 K (899.9 °C)
- Boiling point
- 1743.00 K (1469.8 °C)
How dangerous is it?
One of the most intensely radioactive things people can make, it sprays out both alpha radiation and streams of neutrons.
- RadioactiveImmediate and cumulative
It is a powerful alpha emitter that also pours out neutrons, a penetrating radiation that needs thick shielding to stop. (the neutron output means even a sealed source needs serious shielding, not just distance)
Worked with remotely behind heavy neutron shielding at licensed labs, never by hand.
How it bonds· family overview
Californium (Cf) is an actinide. Like the lanthanides it tends toward a +3 oxidation state, but the early actinides (Th–Am) routinely access +4, +5, +6, even +7 because the 5f electrons are easier to ionize. Most actinides are radioactive; their "bonding" in school is read off the periodic table, not measured in lab.
