Mendelevium (Md)

Unknown

Mendelevium was the first element produced one atom at a time, named after the periodic table's creator, and with [Rn] 5f¹³ 7s², mendelevium-258 (half-life 51.5 days) was synthesized in 1955 by bombarding einsteinium with alpha particles. Only about 20 atoms were initially produced, confirming its actinide chemistry.

Key metrics

Density10.3g/cm³predicted

Melting point1,100Kpredicted

Boiling point1,100Kpredicted

Electronegativity1.3Paulingpredicted

Discovery

1955discovered

Discovered by: Lawrence Berkeley Lab
Reactivity profile: Highly radioactive synthetic element
Reactivity: High
Bonding: Metallic

Electron configuration

\textcolor{#6b7280}{[Rn]}\; \textcolor{#a855f7}{5_{f}^{13}}\; \textcolor{#ef4444}{7_{s}^{2}}

[Rn] 5f13 7s2

Wave function

\Psi_{\text{Md}} \approx \frac{1}{\sqrt{101!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{101}(\mathbf{r}_{101}) \right|

Probability density $|\Psi|^2$ across the Md 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: 188 pmpredicted
Ionization energy: 635 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 K1100 K298 K

predicted

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

425.0nmMd I (blue)Violet60%

475.0nmMd IBlue40%

490.0nmMd I (blue-green)Cyan100%

Dominant line 490.0 nmRange 425–490 nmTransitions 3