What Is Californium?
With symbol Cf and atomic number 98, Californium is a member of the actinides, the bottom row of the standard periodic table.
One of the most expensive substances on Earth. Used as portable neutron source.
As a actinide in Period 7 and Group 3 (Transition Metals), californium's placement on the table reflects its electron configuration of [Rn] 5f¹⁰ 7s², which governs its bonding behavior and the type of compounds it typically forms.
Position on the Periodic Table
Californium is located in Period 7, the bottom row of the standard periodic table, consisting largely of radioactive and synthetic elements.
Within that row, californium sits in Group 3 (Transition Metals), alongside elements that share a similar number of valence electrons and, by extension, similar chemical behavior.
This position is not arbitrary — the periodic table was deliberately organized so that an element's row and column reveal its expected reactivity, bonding pattern, and physical state at a glance.
Physical & Chemical Properties
Californium has an atomic mass of (251) u and a density of 15.1 g/cm³. Its melting point is 900°C and its boiling point is 1472°C.
Californium is radioactive, like every other member of the actinide series, with a nucleus prone to spontaneous decay.
Electron Configuration Explained
Californium's electron configuration is [Rn] 5f¹⁰ 7s², describing how its electrons are distributed across shells and subshells around the nucleus.
Reading the configuration in order shows electrons filling shells of increasing energy, following the standard Aufbau principle that explains how atomic structure builds up across the periodic table.
The outermost (valence) electrons shown in this configuration are what ultimately determine californium's chemical reactivity and the type of bonds it forms with other elements.
History & Discovery
Californium was formally discovered in 1950, G.T. Seaborg, identified through the careful isolation and analytical techniques typical of that era's chemical research.
Many elements from this period were anticipated by Dmitri Mendeleev's periodic table, which successfully predicted gaps corresponding to undiscovered elements well before laboratory instruments existed to confirm them directly.
What Is Californium Used For?
Californium's specific properties make it useful in several applications, including:
- Nuclear reactor start-up
- Cancer treatment
- Metal detection
- Neutron radiography
- Oil well logging
These uses reflect californium's underlying classification as a actinide, since the same properties that define its category in chemistry also determine where it becomes practically useful.
Fun Facts About Californium
- Californium-252 costs about $27 million per gram — one of the most expensive substances on Earth.
- Californium is element number 98 on the periodic table, in Period 7 and Group 3.
- Its standard atomic mass is (251) u, calculated from the natural abundance of its isotopes.
Frequently Asked Questions
What is Californium's atomic number?
Californium has atomic number 98.
What is Californium's chemical symbol?
Californium's symbol is Cf.
What group and period is Californium in?
Californium is in Period 7, Group 3 (Transition Metals).
What is Californium's atomic mass?
Californium's standard atomic mass is (251) u.