Nobelium
[Rn] 5f¹⁴ 7s² · 2 · 8 · 18 · 32 · 32 · 8 · 2
The one actinide for which the +2 oxidation state is more stable than +3: a half-filled 5f shell turns out to be energetically preferable. Nobelium became the subject of one of the longest priority disputes in the history of chemistry.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
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Atomic properties
- Atomic number
- 102
- Atomic mass
- 259 а.е.м. ≈
- Electron configuration
- [Rn] 5f¹⁴ 7s²
- Electrons per shell
- 2 · 8 · 18 · 32 · 32 · 8 · 2
- Block
- f-block
- Group
- no data
- Period
- 7
- Electronegativity (Pauling)
- 1.3
- Electronegativity (Allen)
- 1.3
- Atomic radius
- 246 pm
- Covalent radius
- 176 pm
- Van der Waals radius
- 246 pm
- Ionisation energy 1
- 642 kJ/mol
- Electron affinity
- -223.2 kJ/mol
- Common oxidation states
- +2
- Oxidation states
- +2, +3
Physical properties
- State at 25 °C
- solid
- Density
- 9.9 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 |
|---|---|---|---|
| 255No | — | 3.1 min | α |
| 259No | — | 58 min | α |
Nobelium-259, half-life 58 minutes, is the longest-lived. Its chemistry was studied on nobelium-255 at 3.1 minutes.
Discovery
- Year of discovery
- 1966
- Discovered by
- Joint Institute for Nuclear Research
- Where
- Dubna, USSR
- Origin of the name
- after Alfred Nobel
History
A synthesis was announced in Stockholm in 1957, but the result did not hold up. Dubna and Berkeley made independent claims between 1958 and 1966; IUPAC awarded priority to Dubna in 1997 while keeping the Swedish name.
Where it occurs
Absent from nature.
How it is produced
By nuclear fusion in an accelerator, bombarding lead or curium with ions. 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 into the stability of oxidation states in heavy actinides
Curiosities
- The name was given in Stockholm for a discovery that had not happened — and it stuck.
- Nobelium is the only actinide whose +2 state beats +3.
- The priority dispute between Dubna and Berkeley over elements 102 to 106 ran for thirty years and is known as the Transfermium Wars.
- Alfred Nobel had nothing to do with transuranium chemistry, yet an element carries his name.