Californium Facts

Chemical & Physical Properties of Californium

This is the electron configuration of a californium atom.
Electron configuration of a californium atom.

GregRobson/CC BY-SA 2.0 UK/Wikimedia Commons 

by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated July 22, 2018

Californium is a radioactive rare earth element that can be used as a neutron source.

Atomic Number: 98
Symbol: Cf
Atomic Weight: 251.0796
Discovery: G.T. Seaborg, S.G. Tompson, A. Ghiorso, K. Street Jr. 1950 (United States)
Word Origin: State and University of California

Properties: Californium metal has not been produced. Californium (III) is the only ion stable in aqueous solutions. Attempts to reduce or oxidize californium (III) have been unsuccessful. Californium-252 is a very strong neutron emitter.

Uses: Californium is an efficient neutron source. It is used in neutron moisture gauges and as a portable neutron source for metal detection.

Isotopes: The isotope Cf-249 results from the beta decay of Bk-249. Heavier isotopes of californium are produced by intense neutron irradiation by the reactions. Cf-249, Cf-250, Cf-251, and Cf-252 have been isolated.

Sources: Californium was first produced in 1950 by bombarding Cm-242 with 35 MeV helium ions.

Electron Configuration

[Rn] 7s2 5f10

Californium Physical Data

Element Classification: Radioactive Rare Earth (Actinide)
Density (g/cc): 15.1
Melting Point (K): 900
Atomic Radius (pm): 295
Pauling Negativity Number: 1.3
First Ionizing Energy (kJ/mol): (610)
Oxidation States: 4, 3

References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)