Mendelevium
[Rn] 5f¹³ 7s² · 2 · 8 · 18 · 32 · 31 · 8 · 2
The element named after the author of the periodic law. Mendelevium was made by bombarding a target of just a thousand einsteinium atoms and detecting one atom per experiment.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 101
- Atomic mass
- 258 а.е.м. ≈
- Electron configuration
- [Rn] 5f¹³ 7s²
- Electrons per shell
- 2 · 8 · 18 · 32 · 31 · 8 · 2
- Block
- f-block
- Group
- no data
- Period
- 7
- Electronegativity (Pauling)
- 1.3
- Electronegativity (Allen)
- 1.3
- Atomic radius
- 246 pm
- Covalent radius
- 173 pm
- Van der Waals radius
- 246 pm
- Ionisation energy 1
- 635 kJ/mol
- Electron affinity
- 93.9 kJ/mol
- Common oxidation states
- +3
- Oxidation states
- +2, +3
Physical properties
- State at 25 °C
- solid
- Density
- 10.3 g/cm³ ≈
- Melting point
- 1 100 K · 826.9 °C ≈
- Boiling point
- no data
- Speed of sound
- no data
Thermal properties
- Heat of fusion
- no data
- Heat of vaporisation
- no data
- Specific heat capacity
- no data
- Thermal conductivity
- no data
Mechanical properties
- Young's modulus
- no data
- Shear modulus
- no data
- Bulk modulus
- no data
- Poisson ratio
- no data
- Mohs hardness
- no data
- Brinell hardness
- no data
Electrical and magnetic properties
- Electrical resistivity
- no data
- Magnetic ordering
- paramagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- no data
Crystal structure
- Crystal structure
- face-centred cubic (fcc)
- Lattice constants
- no data
Abundance
- In the crust
- does not occur
- In the ocean
- does not occur
- In the universe
- does not occur
- In the human body
- does not occur
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 258Md | — | 51.5 d | α |
| 260Md | — | 31.83 d | СД |
Mendelevium-258, half-life 51.5 days, is the longest-lived. Mendelevium-256, the first made, lives 77 minutes.
Discovery
- Year of discovery
- 1955
- Discovered by
- Ghiorso, Harvey, Choppin, Thompson and Seaborg
- Where
- Berkeley, USA
- Origin of the name
- after Dmitri Mendeleev, author of the periodic law
History
Ghiorso, Harvey, Choppin, Thompson and Seaborg synthesised mendelevium at Berkeley in 1955. The first run produced seventeen atoms. The name drew objections at the height of the Cold War but was accepted.
Where it occurs
Absent from nature.
How it is produced
By alpha bombardment of einsteinium in an accelerator. It is made one atom at a time.
Role in living things
No biological role.
Safety
Only single atoms are ever handled.
Uses
Fundamental research: mendelevium was the first element whose chemistry was studied at the single-atom level
Curiosities
- Mendelevium honours Dmitri Mendeleev — the only element named after the author of the table itself.
- The recoil technique developed for mendelevium became the standard for all subsequent superheavy chemistry.
- The first experiment registered seventeen atoms, one at a time.
- Proposing a Russian scientist's name in 1955 was a deliberate political gesture by American physicists.