About

Mendelevium is named in honor of Dmitri Mendeleev, the Russian chemist who is considered the father of the periodic table. It was the first element to be synthesized one atom at a time by bombarding einsteinium with alpha particles. It is a highly radioactive synthetic element used only to study its own chemical properties and the limits of the periodic table.

Atomic Properties

Atomic Number101

Atomic Weight258 u

Neutrons (common)157

Electron Configuration[Rn] 5f¹³ 7s²

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹³ 6s² 6p⁶ 7s²

Electrons per Shell2, 8, 18, 32, 31, 8, 2

Electronegativity1.3

Electron Affinity9.7 kJ/mol

Oxidation States+3, +2, +1

Ionic Radius90 pm

Periodic Table Position

Group3

Period7

BlockF

Chemical SeriesActinoids

Physical Properties

State at STPsolid

Crystal Structurefcc

Magnetic Orderingparamagnetic

Thermal Properties

Melting Point1,100 K

Heat of Fusion11 kJ/mol

Discovery

Discovered byAlbert Ghiorso, Glenn T. Seaborg, Gregory Robert Choppin, Bernard G. Harvey, Stanley G. Thompson

Discovery Year1,955

Occurrencesynthetic

CAS Number7440-11-1

Electron Configuration

Energy

↿⇂

1s

↿⇂

2s

↿⇂

2p

↿⇂

3s

↿⇂

3p

↿⇂

4s

↿⇂

3d

↿⇂

4p

↿⇂

5s

↿⇂

4d

↿⇂

5p

↿⇂

6s

↿⇂

4f

↿⇂

5d

↿⇂

6p

↿⇂

7s

↿⇂

↿

5f

6d

7p

Isotopes of Mendelevium

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
²⁵⁸Md	258.098430	—	51.59 d	Electron Capture