Fermium

Atomic number

100

Atomic mass (u)

257.09511

Category

Actinide

Standard state

Solid

Melting point

1526.85 °C (1800 K)

Boiling point

Not reported

Density (g/cm³)

Not reported in this source

Electronegativity (Pauling)

1.3

Electron configuration

[Rn] 5f12 7s2

Oxidation states

+3

Atomic radius (pm)

Not reported in this source

First ionization energy (eV)

6.50

Discovery & recognition

Discovery year / period (PubChem)

1952

Discovery credited to (RSC)

Albert Ghiorso and colleagues

Date or period recorded by RSC

1953

Discovery place

Pacific thermonuclear-test debris

An ancient date does not identify a first human discovery. Different references may date observation, isolation and formal recognition differently.

Natural occurrence & production

This transuranium element is primarily produced through nuclear reactions in reactors or particle accelerators. Some transuranium elements also occur naturally in extremely small traces; that is different from a mineable deposit.

“Fermium can be obtained, in microgram quantities, from the neutron bombardment of plutonium in a nuclear reactor.”

Royal Society of Chemistry · occurrence excerpt ↗

Continue the research

Reference values are not product specifications. Blank values have not been estimated. For superheavy elements, some properties and family assignments are theoretical or incompletely measured.