98
Cf
Californium
251
Californium (Cf)
ActinidePeriod 7f-block-blockRadioactive
Californium is a radioactive metallic chemical element with symbol Cf and atomic number 98. The element was first made in 1950 at the University of California Radiation Laboratory in Berkeley, by bombarding curium with alpha particles (helium-4 ions). It is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all the elements that have been produced in amounts large enough to see with the unaided eye (after einsteinium).
Latin name: Californium
Atomic Number
98
Atomic Mass
251 g/mol
Phase (STP)
Solid
Electron Config.
[Rn] 5f¹⁰ 7s²
General
SymbolCf
Atomic Number98
Atomic Mass251 g/mol
CategoryActinide
Period7
Blockf-block
Electron Configuration[Rn] 5f¹⁰ 7s²
Valence Electrons12
Coloursilvery-white (radioactive)
Appearancesilvery
CAS NumberCAS7440-71-3
Physical Properties
Phase (STP)Solid
Density15.1 g/cm³
Melting Point626.85°C · 1160.33°F · 900.00 K
Boiling Point1469.85°C · 2677.73°F · 1743.00 K
Atomic Properties
Atomic Radius245 pm
Electronegativity1.3 Pauling
Ionization Energy608 kJ/mol
Oxidation States+3, +2
Ion ChargeCf2+/Cf3+
Crystal Structure
Crystal Structureface-centered cubic
Nuclear & Hazards
RadioactiveYes
Half-life898 years (Cf-251)
Abundance
In Earth's Crust0.00000000000001%
Discovery & History
Discovery Year1950
Discovered ByStanley G. Thompson, Kenneth Street Jr., Albert Ghiorso, and Glenn T. Seaborg
Country of DiscoveryUSA
Isotopes of Californium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Cf-249 | — | 351 years | α |
| Cf-250 | — | 13.08 years | α, SF |
| Cf-251 | — | 898 years | α |
| Cf-252 | — | 2.645 years | α, SF |