All practice pages/Interatomic theory/Elements
Element 98, an actinide
Named for California, and a powerful source of neutrons that can start up reactors and find gold.
Period 7, in the actinide row set below the main table. The other actinides are tinted, and every cell opens its own article.
Californium has 98 electrons, one for every proton, so the atom carries no charge. Below are the same 98 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁰ 6s² 6p⁶ 7s²
Short form: [Rn] 5f¹⁰ 7s², where [Rn] stands for the 86 electrons radon already has.
That list runs by shell. In the order the subshells fill it reads [Rn] 7s² 5f¹⁰, because a subshell fills by its energy, not by its shell number.
The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 4 here is 4s² 4p⁶ 4d¹⁰ 4f¹⁴, and 2 + 6 + 10 + 14 is 32.
Californium sits in period 7 and has 7 shells. The period number counts the shells.
The outer shell holds 2 electrons. Those are the ones californium can lose, gain or share, so they are the ones that decide what it bonds with.
Radioactive, like every actinide. It gives up electrons to form positive ions.
Not found in nature; made in small amounts in high-flux reactors.
Stanley Thompson, Kenneth Street Jr., Albert Ghiorso and Glenn Seaborg made it in 1950 at Berkeley by bombarding curium with alpha particles, and named it after the state and its university.
Californium-252 splits on its own and releases neutrons, so a few micrograms can start up nuclear reactors, measure water and oil in rock, find gold and silver ores, scan luggage for explosives, and treat some cancers. Californium-249 was the target used to make oganesson.
An intense neutron source; even micrograms need heavy shielding.