Atomic Number
100
Element 100
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 Mass
257 u
Category
Actinide
Period
7
Group
Actinide series
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
Why Fermium Matters
Fermium helps connect atomic number 100, actinide behavior, period 7 trends, and electron shell structure. Its solid phase, atomic mass of 257 u, and electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹² make it useful for comparing bonding patterns across the periodic table.
Discovery and Occurrence
Fermium was discovered 1952 by Albert Ghiorso, Stanley G. Thompson, Glenn T. Seaborg, Bernard G. Harvey. 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.
Safety and Handling Context
Fermium has radioactive isotopes or is commonly discussed with radioactive materials. Use this page as an educational reference; real samples require qualified supervision and controlled handling.
Related Elements
Frequently Asked Questions
- What is the atomic number of Fermium?
- Fermium has atomic number 100, which means a neutral atom has 100 protons and 100 electrons.
- What is the chemical symbol for Fermium?
- The chemical symbol for Fermium is Fm.
- What category is Fermium in?
- Fermium is classified as a actinide and sits in period 7 of the periodic table.
Explore Fermium in 3D
Use the interactive table above to rotate atomic models, compare periodic trends, and move from Fermium to neighboring elements without losing your place.