100 Fm 257

Fermium

actinide

Properties

Atomic number
100
Atomic mass
257 u
Category
actinide
Group
f-block
Period
7
Block
f-block
State (room temp)
Solid
Outer-shell electrons
2
Electronegativity
1.3 (Pauling)
Density
Melting point
1526.85 °C
Boiling point

Electron configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹²

Noble-gas shorthand: [Rn] 5f¹² 7s²

Electrons per shell: 2, 8, 18, 32, 30, 8, 2 — that's 2 in the outermost shell.

See how electron configuration is built →

Fm
Bohr model — outer-shell electrons in blue

About Fermium

Fermium is a synthetic element with symbol Fm and atomic number 100. It is a member of the actinide series. It is the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic quantities, although pure fermium metal has not yet been prepared.

Position in the periodic table

Open the interactive periodic table →

Data compiled from Wikipedia, PubChem, and IUPAC. Source.