Nobelium (No)

Unknown

Nobelium is the first actinide to favor a +2 oxidation state instead of the typical +3, and with a completely filled 5f¹⁴ shell, nobelium-259 (half-life 58 minutes) uniquely stabilizes the No²⁺ ion in aqueous solution. This behavior marks the end of the actinide series where the 5f shell becomes fully occupied.

Key metrics

Density9.9g/cm³predicted

Melting point1,100Kpredicted

Boiling point1,050Kpredicted

Electronegativity1.3Paulingpredicted

Discovery

1958discovered

Discovered by: Joint Institute for Nuclear Research
Reactivity profile: Radioactive synthetic metal
Reactivity: High
Bonding: Metallic

Electron configuration

\textcolor{#6b7280}{[Rn]}\; \textcolor{#a855f7}{5_{f}^{14}}\; \textcolor{#ef4444}{7_{s}^{2}}

[Rn] 5f14 7s2

Wave function

\Psi_{\text{No}} \approx \frac{1}{\sqrt{102!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{102}(\mathbf{r}_{102}) \right|

Probability density $|\Psi|^2$ across the No valence shell.

Crystal structure

Hexagonal Close-Packed

Lattice constantsa 1.00 · b 1.00 · c 1.63

Cell anglesα 90° · β 90° · γ 120°

Coordination number12

Atoms per cell2

Atomic packing factor0.74

Physical properties

Atomic radius: 190 pmpredicted
Ionization energy: 642 kJ/molpredicted
Electron affinity: 0 kJ/molpredicted
Crystal structure: Hexagonal close-packed (predicted)

Oxidation statespredicted

+2+3

Acid/base

Basic

Strongly acidicStrongly basic

State at 25 °CSolid

1100 K1050 K298 K

predicted

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

422.0nmNo I (blue)Violet60%

470.0nmNo IBlue40%

485.0nmNo I (blue-green)Blue100%

Dominant line 485.0 nmRange 422–485 nmTransitions 3