ElementsWhat is mendelevium?
Mendelevium is a radioactive element made a few atoms at a time in particle accelerators.
What is mendelevium used for?
Research only.
Where the name comes from
In honour of Dmitri Mendeleev, who made the first widely accepted periodic table.
Key facts
- Symbol
- Md
- Atomic number
- 101
- Atomic mass
- 258.09843 u
- Family
- Actinide
- Period
- 7
- Group
- none (f-block)
- Block
- f
- State at room temperature
- Solid
- Melting point
- 826.9 °C (1,100 K, 1,520 °F)
- Boiling point
- not measured
- Density
- not measured
- Electrons per shell
- 2, 8, 18, 32, 31, 8, 2
- Electron configuration
- [Rn]7s2 5f13
- Common oxidation states
- +3, +2
- Electronegativity (Pauling)
- 1.3
- First ionisation energy
- 6.58 eV
- Electron affinity
- no value
- Atomic radius (van der Waals)
- no value
- Discovered
- 1955
Place in the periodic table
Mendelevium is element number 101. It sits in period 7 (row 7) of the periodic table, in the separate row of actinides drawn below the main table, and belongs to the f-block. Just before it comes fermium (100), and just after it comes nobelium (102).
Family: Actinides.
Physical properties
At room temperature mendelevium is a solid. Its melting point is about 826.9 °C. Its boiling point has not been measured reliably.
Inside the atom
An atom of mendelevium has 101 protons in its nucleus and, when neutral, 101 electrons around it. The electrons are arranged in 7 shells: 2, 8, 18, 32, 31, 8, 2. The outermost shell holds 2 electrons. Written in full, the electron configuration is [Rn]7s2 5f13.
Its electronegativity on the Pauling scale is 1.3. This number shows how strongly an atom pulls shared electrons towards itself: fluorine, the strongest, is 3.98. Removing one electron from an atom takes 6.58 electronvolts (about 635 kilojoules per mole). One mole of mendelevium weighs 258.09843 grams, so a single gram contains about 2.33 × 1021 atoms.
The ring picture is a simple model that only counts the electrons in each shell. Real atoms do not look like this.
Next steps
- Work out the weight of a compound that contains mendelevium with the molar mass calculator.
- Compare it with every other element in the sortable list.
- Test yourself with the symbol quiz.
Figures on this page are from PubChem (U.S. National Library of Medicine), as downloaded on 11 November 2026. See About and data sources.