98[251]CfCalifornium
Californium (Cf) — element 98actinide · period 7
Californium is a chemical element with the symbol Cf and atomic number 98. It is an actinide in period 7 of the periodic table (the f-block), with a standard atomic mass of [251] u. At room temperature (25 °C) californium is a solid.
💡 Known for: Californium-252 is a powerful neutron source used to start nuclear reactors and to analyse oil wells.
# Californium properties
| Symbol | Cf |
|---|---|
| Atomic number | 98 |
| Atomic mass | [251] u |
| Category | actinide |
| Group | — (f-block, no group number) |
| Period | 7 |
| Block | f-block |
| Electron configuration | [Rn] 5f¹⁰ 7s² |
| Full configuration | 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁰ 6s² 6p⁶ 7s² |
| Electrons per shell | 2, 8, 18, 32, 28, 8, 2 |
| Protons / electrons | 98 / 98 |
| State at 25 °C | solid |
| Melting point | 1173 K (899.9 °C, 1651.7 °F) |
| Boiling point | 1743 K (1469.8 °C, 2677.7 °F) |
| Density | 15.1 g/cm³ |
| Electronegativity (Pauling) | 1.3 |
| First ionization energy | 6.282 eV |
| Atomic radius | 169 pm |
| Discovered | 1950 |
# Electron configuration of californium
The electron configuration of californium is [Rn] 5f¹⁰ 7s², written out in full as 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁰ 6s² 6p⁶ 7s². Its 98 electrons fill 7 shells as 2, 8, 18, 32, 28, 8, 2, so the outermost shell holds 2 electrons.
# Related elements
BkBerkeliumprevious elementEsEinsteiniumnext elementAcActiniumactinideThThoriumactinidePaProtactiniumactinideUUraniumactinideNpNeptuniumactinidePuPlutoniumactinideAmAmericiumactinideCmCuriumactinide
# Californium FAQ
What is the atomic number of californium?
The atomic number of californium is 98: every californium atom has 98 protons in its nucleus. Its symbol is Cf.
What is the atomic mass of californium?
The standard atomic mass of californium is [251] u (the mass number of its longest-lived isotope, since it has no stable isotopes).
What is the electron configuration of californium?
Californium's electron configuration is [Rn] 5f¹⁰ 7s² (1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁰ 6s² 6p⁶ 7s²), with 2, 8, 18, 32, 28, 8, 2 electrons per shell.
Is californium a metal?
Yes. Californium is an actinide, one of the metals.
What is the melting point of californium?
Californium melts at 1173 K (899.9 °C, 1651.7 °F) and boils at 1743 K (1469.8 °C, 2677.7 °F).
What is californium used for / known for?
Californium-252 is a powerful neutron source used to start nuclear reactors and to analyse oil wells.