101
Md
Mendelevium
258
Mendelevium (Md)
ActinidePeriod 7f-block-blockRadioactive
Mendelevium is a synthetic element with chemical symbol Md (formerly Mv) and atomic number 101. A metallic radioactive transuranic element in the actinide series, it is the first element that currently cannot be produced in macroscopic quantities through neutron bombardment of lighter elements. It is the antepenultimate actinide and the ninth transuranic element.
Latin name: Mendelevium
Atomic Number
101
Atomic Mass
258 g/mol
Phase (STP)
Solid
Electron Config.
[Rn] 5f¹³ 7s²
General
SymbolMd
Atomic Number101
Atomic Mass258 g/mol
CategoryActinide
Period7
Blockf-block
Electron Configuration[Rn] 5f¹³ 7s²
Valence Electrons15
Coloursilvery (radioactive)
Physical Properties
Phase (STP)Solid
Atomic Properties
Atomic Radius246 pm
Electronegativity1.3 Pauling
Ionization Energy635 kJ/mol
Oxidation States+2, +3
Ion ChargeMd2+/Md3+
Nuclear & Hazards
RadioactiveYes
Half-life51.5 days (Md-258)
Abundance
In Earth's Crust0.000000000000001%
Discovery & History
Discovery Year1955
Discovered ByAlbert Ghiorso and co-workers
Country of DiscoveryUSA
Isotopes of Mendelevium
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Md-257 | — | 5.52 hours | α, EC |
| Md-258 | — | 51.5 days | α |
| Md-260 | — | 31.8 days | SF, α |