100 · Fm

Fermium

Identified in 1952 in the same debris as einsteinium.

Identity

Atomic number: 100
Symbol: Fm
Canonical name: Fermium
Category: actinide
Group: unassigned
Period: 7
Block: f

Series set apart from the main table. Whether group 3 is lanthanum or lutetium (actinium or lawrencium) is still discussed, so the group is left empty.

Properties

These quantities come from the Periodic Table JSON compilation. They have not yet been checked, one by one, against CIAAW atomic weights or NIST measurements. A value marked estimated is not a measurement.

Atomic mass: [257] No standard atomic weight. The number shown is the conventional mass number used in tables, not a measured mass in u.
Electron configuration: [Rn] 5f12 7s2
Electrons per shell: 2, 8, 18, 32, 30, 8, 2
Standard state: solid
Melting point: 1,800 K
Electronegativity: 1.3 Pauling
First ionization energy: 627 kJ/mol
Electron affinity: 33.96 kJ/mol

Notable isotopes

This summary is not an inventory of every isotope.

Conventional mass number: 257

History

Ivy Mike debris

Identification · confirmed · 1952

Fermium is identified in the same debris as einsteinium. The team is wider than the single name kept here for the index.

Evidence: Debris from the Ivy Mike test.

See the element timeline

Etymology

Theme: scientist
Language: italien
Root: Fermi
Meaning: Enrico Fermi

Scientists

Albert Ghiorso

Places and institutions

Berkeley Radiation Laboratory, later Lawrence Berkeley National Laboratory

Enewetak — historical setting : Trust Territory of the Pacific Islands — present country : Marshall Islands Site of the Ivy Mike test, whose debris yielded einsteinium and fermium.