Fermium (Fm)

Fermium is a synthetic element with symbol Fm and atomic number 100. It is an actinide and 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.

Atomic Number

100

Atomic Mass

257 u

Category

actinide

Phase

solid

Density

9.7 g/cm³

Electron Shells

2, 8, 18, 32, 30, 8, 2

Atomic Structure

Protons: 100 • Electrons: 100 • Neutrons: Varies by isotope

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

Discovery

1952 • Albert Ghiorso, Stanley G. Thompson, Glenn T. Seaborg, Bernard G. Harvey