Our Elements
Menu

Fermium

Element 100 · Actinide

Specimen

Atomic number
100
Atomic mass
[257]
State at room temperature
Solid
Melting point
1,527 °C
Boiling point
Unknown
Density
Unknown
Discovered
1952

Mass number of the longest-lived isotope, from IUPAC.1 Other physical data from PubChem.2

Can I eat it?

In food and water
Never made in amounts you could eat. Reactors make fermium only in very small amounts. All its isotopes are short-lived. Fermium has no use outside research. 3

See every element.

The atom

Fm
ShellElectrons
1 (K) 2
2 (L) 8
3 (M) 18
4 (N) 32
5 (O) 30
6 (P) 8
7 (Q) outermost 2
Total100

Configuration [Rn] 5f¹² 7s²

5f ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↓ ↑ ↑
7s ↑ ↓
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 100 protons. The outermost shell is shown in red. Electrons do not travel on rings: they fill orbitals, regions where an electron is likely to be found. The boxes are those orbitals for the electrons outside the Rn core, with one arrow per electron.

Related elements

Actinides
Ac Actinium Th Thorium Pa Protactinium U Uranium Np Neptunium Pu Plutonium Am Americium Cm Curium Bk Berkelium Cf Californium Es Einsteinium Md Mendelevium No Nobelium Lr Lawrencium

New elements by e-mail

Sources

  1. 1

    IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), 2024. Radioactive Elements .

    Mass number and half-life of the longest-lived isotope of the 34 elements with no standard atomic weight.

  2. 2

    National Center for Biotechnology Information (PubChem), 2026. Periodic Table of Elements .

    Electron configuration, melting and boiling points, density and discovery year for all 118 elements.

  3. 3

    Los Alamos National Laboratory, Periodic Table of Elements, 2026. Fermium .

    • Because of the short half-lives of all fermium isotopes, and the fact that only very small amounts of fermium can be produced, fermium has no applications beyond basic scientific research.