Fermium (Fm)
Fermium (Fm) is element 100 of the periodic table, an actinide in period 7, in the f-block. It has no stable isotope and no standard atomic weight; 257 is the mass number of its longest-lived isotope. At room temperature it is a solid.
| Atomic number | 100 |
|---|---|
| Symbol | Fm |
| Standard atomic weight | [257] (mass number of the longest-lived isotope) |
| Molar mass | [257] g/mol |
| Category | Actinide |
| Group | f-block (actinide series) |
| Period | 7 |
| Block | f-block |
| Electron configuration | [Rn] 5f12 7s2 |
| Oxidation states | +3 |
| Electronegativity (Pauling) | 1.3 |
| Atomic radius (van der Waals) | — |
| First ionisation energy | 6.5 eV (627.2 kJ/mol) |
| Electron affinity | — |
| State at room temperature | Solid |
| Melting point | 1800 K (1526.85 °C) |
| Boiling point | — |
| Density | — |
| Discovered | 1952 |
Actinides
Ac · ActiniumTh · ThoriumPa · ProtactiniumU · UraniumNp · NeptuniumPu · PlutoniumAm · AmericiumCm · CuriumBk · BerkeliumCf · CaliforniumEs · EinsteiniumMd · MendeleviumNo · Nobelium
Calculate with Fermium
Atomic weight: IUPAC CIAAW — no standard atomic weight; mass number in brackets. Other properties: PubChem (U.S. National Library of Medicine, public domain). Values such as melting point and radius depend on how they were measured; check a data book for precise work.