Californium (Cf)
Actinide · f-block · period 7
Silvery-white radioactive metal, malleable enough to cut.
Californium (symbol Cf) is chemical element number 98, a actinide in the actinide series (f-block), period 7 of the periodic table. Its standard atomic weight is (251) and its electron configuration is [Rn] 5f10 7s2. At room temperature it is a solid, and it is radioactive. Named after the state and university of California.
Properties
| Atomic number | 98 |
|---|---|
| Atomic mass | (251) |
| Category | Actinide |
| Block | f-block |
| Group · Period | f-block series · 7 |
| Electron configuration | [Rn] 5f10 7s2 |
| Electrons per shell | 2, 8, 18, 32, 28, 8, 2 |
| State at 25 °C | solid |
| Melting point | 1173 K |
| Boiling point | 1743 K |
| Density | 15.1 g/cm³ |
| Electronegativity (Pauling) | 1.3 |
| Radioactive | Yes — no stable isotope |
| Origin | synthetic |
| Discovered | 1950 · Thompson, Street, Ghiorso & Seaborg |
Key facts about Californium
- Named after the state and university of California.
- One microgram releases about 2.3 million neutrons every second.
- That makes it a portable neutron source to start reactors, scan cargo and find gold and oil underground.
- One of the few synthetic elements made in weighable (milligram) amounts and actually sold.
What Californium is used for
Portable neutron sources for reactor start-up, oil-well logging, cargo scanning, cancer treatment, ore analysis.
Where it sits in the periodic table
Californium is in the actinide series, period 7, of the f-block. Its electron configuration [Rn] 5f10 7s2 means its outermost shell holds 2 electrons, which is what places it here and explains much of its chemistry. See Californium on the interactive table →
Californium — frequently asked questions
What is Californium used for?
Portable neutron sources for reactor start-up, oil-well logging, cargo scanning, cancer treatment, ore analysis.
Is Californium radioactive?
Yes. Californium has no stable isotope, so every form of it is radioactive.
What is the electron configuration of Californium?
Californium has the electron configuration [Rn] 5f10 7s2, which is 2, 8, 18, 32, 28, 8, 2 electrons per shell.
What group and period is Californium in?
Californium is in the actinide series (f-block), period 7, in the f-block. Its outer shell holds 2 electrons.
Who discovered Californium?
Californium was discovered in 1950 by Thompson, Street, Ghiorso & Seaborg.