Mendelevium

Mendelevium (Md)

Radioactive metallic transuranic element. Belongs to the actinoid series. Only known isotope, Md-256 has a half-life of 1.3 hours. First identified by Glenn T. Seaborg, Albert Ghiorso and associates in 1955. Alternative name Unnilunium has been proposed. Named after the 'inventor' of the periodic table, Dmitri Mendeleev.
Atomic Number101
Atomic Weight258
Mass Number244
Group
Period7
Blockf
Protons101 p+
Neutrons143 n0
Electrons101 e-
Electron shell 101 Mendelevium.svg Animated Bohr Model of Md (Mendelevium) Enhanced Bohr Model of Md (Mendelevium) Bohr Model: Md (Mendelevium) Orbital Diagram of Md (Mendelevium)

Properties

Atomic Radius
Molar Volume
Covalent Radius
173 pm
Metallic Radius
Ionic Radius
109.5 pm
Crystal Radius
123.5 pm
Van der Waals Radius
246 pm
Density
10.3 g/cm³
Energy
Proton Affinity
Electron Affinity
Ionization Energy
Heat of Vaporization
Heat of Fusion
Heat of Formation
Electrons
Electron Shells2, 8, 18, 32, 31, 8, 2
Valence Electrons3
Electron Configuration[Rn] 5f13 7s2
Oxidation States2, 3
Electronegativity
Electrophilicity
Phases
PhaseSolid
Gas Phase
Boiling Point
Melting Point
1,100.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Color
Colorless
Appearance
Refractive Index
Thermodynamic Properties
Thermal Conductivity
Thermal Expansion
Molar Heat Capacity
Specific Heat Capacity
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
Type
Electrical Conductivity
Electrical Resistivity
Superconducting Point
Magnetism
Type
Magnetic Susceptibility (Mass)
Magnetic Susceptibility (Molar)
Magnetic Susceptibility (Volume)
Magnetic Ordering
Curie Point
Neel Point
Structure
Crystal Structure ()
Lattice Constant
Lattice Angles
Mechanical Properties
Hardness
Bulk Modulus
Shear Modulus
Young Modulus
Poisson Ratio
Speed of Sound
Classification
CategoryActinides, Actinides
CAS Group
IUPAC Group
Glawe Number45
Mendeleev Number38
Pettifor Number36
Geochemical Class
Goldschmidt Classsynthetic
Other
Gas Basicity
Dipole Polarizability
109 ± 20 a₀
C6 Dispersion Coefficient
Allotropes
Neutron Cross Section
Neutron Mass Absorption
Quantum Numbers2F7/2
Space Group ()

Isotopes of Mendelevium

Stable Isotopes0
Unstable Isotopes19
Radioactive Isotopes19

244Md

AbundanceRadioactive ☢️
Relative Atomic Mass
244.081157 ± 0.000402 Da
Mass Number244
G-Factor
Half Life
0.36 ± 0.14 s
Spin3
Quadrupole Moment
Discovery Year2020
Parity+

244Md Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%
β+ SF (β+-delayed fission)14%

245Md

AbundanceRadioactive ☢️
Relative Atomic Mass
245.080864 ± 0.000279 Da
Mass Number245
G-Factor
Half Life
0.38 ± 0.1 s
Spin7/2
Quadrupole Moment
Discovery Year1996
Parity-

245Md Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)%

246Md

AbundanceRadioactive ☢️
Relative Atomic Mass
246.081713 ± 0.000279 Da
Mass Number246
G-Factor
Half Life
0.92 ± 0.18 s
Spin1
Quadrupole Moment
Discovery Year1996
Parity-

246Md Decay Modes
Decay ModeIntensity
α (α emission)100%

247Md

AbundanceRadioactive ☢️
Relative Atomic Mass
247.08152 ± 0.000223 Da
Mass Number247
G-Factor
Half Life
1.19 ± 0.09 s
Spin7/2
Quadrupole Moment
Discovery Year1981
Parity-

247Md Decay Modes
Decay ModeIntensity
α (α emission)100%
SF (spontaneous fission)0.1%

248Md

AbundanceRadioactive ☢️
Relative Atomic Mass
248.082607 ± 0.000198 Da
Mass Number248
G-Factor
Half Life
7 ± 3 s
Spin
Quadrupole Moment
Discovery Year1973
Parity

248Md Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)80%
α (α emission)20%
β+ SF (β+-delayed fission)0.05%

249Md

AbundanceRadioactive ☢️
Relative Atomic Mass
249.082857155 ± 0.000176516 Da
Mass Number249
G-Factor
Half Life
25.6 ± 0.9 s
Spin7/2
Quadrupole Moment
Discovery Year1973
Parity-

249Md Decay Modes
Decay ModeIntensity
α (α emission)75%
β+ (β+ decay; β+ = ϵ + e+)%

250Md

AbundanceRadioactive ☢️
Relative Atomic Mass
250.084164934 ± 0.000097606 Da
Mass Number250
G-Factor
Half Life
54 ± 4 s
Spin2
Quadrupole Moment
Discovery Year1973
Parity-

250Md Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)93%
α (α emission)7%
β+ SF (β+-delayed fission)0.026%

251Md

AbundanceRadioactive ☢️
Relative Atomic Mass
251.084774287 ± 0.00002031 Da
Mass Number251
G-Factor
Half Life
4.21 ± 0.23 m
Spin7/2
Quadrupole Moment
Discovery Year1973
Parity-

251Md Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)%
α (α emission)10%

252Md

AbundanceRadioactive ☢️
Relative Atomic Mass
252.086385 ± 0.000098 Da
Mass Number252
G-Factor
Half Life
2.3 ± 0.8 m
Spin1
Quadrupole Moment
Discovery Year1973
Parity+

252Md Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
α (α emission)%

253Md

AbundanceRadioactive ☢️
Relative Atomic Mass
253.087143 ± 0.000034 Da
Mass Number253
G-Factor
Half Life
12 ± 8 m
Spin7/2
Quadrupole Moment
Discovery Year1992
Parity-

253Md Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
α (α emission)0.7%

254Md

AbundanceRadioactive ☢️
Relative Atomic Mass
254.08959 ± 0.000107 Da
Mass Number254
G-Factor
0
Half Life
10 ± 3 m
Spin0
Quadrupole Moment
0
Discovery Year1970
Parity-

254Md Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)100%
α (α emission)%

255Md

AbundanceRadioactive ☢️
Relative Atomic Mass
255.091081702 ± 0.000005976 Da
Mass Number255
G-Factor
Half Life
27 ± 2 m
Spin7/2
Quadrupole Moment
Discovery Year1958
Parity-

255Md Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)93%
α (α emission)7%
SF (spontaneous fission)%

256Md

AbundanceRadioactive ☢️
Relative Atomic Mass
256.093888 ± 0.000133 Da
Mass Number256
G-Factor
Half Life
77.7 ± 1.8 m
Spin1
Quadrupole Moment
Discovery Year1955
Parity-

256Md Decay Modes
Decay ModeIntensity
β+ (β+ decay; β+ = ϵ + e+)90.8%
α (α emission)9.2%
SF (spontaneous fission)3%

257Md

AbundanceRadioactive ☢️
Relative Atomic Mass
257.095537343 ± 0.000001683 Da
Mass Number257
G-Factor
Half Life
5.52 ± 0.05 h
Spin7/2
Quadrupole Moment
Discovery Year1965
Parity-

257Md Decay Modes
Decay ModeIntensity
ϵ (electron capture)85%
α (α emission)15%
SF (spontaneous fission)%

258Md

AbundanceRadioactive ☢️
Relative Atomic Mass
258.098433634 ± 0.000003729 Da
Mass Number258
G-Factor
Half Life
51.59 ± 0.29 d
Spin8
Quadrupole Moment
Discovery Year1970
Parity-

258Md Decay Modes
Decay ModeIntensity
α (α emission)100%
β+ (β+ decay; β+ = ϵ + e+)0.0015%
β (β decay)0.0015%

259Md

AbundanceRadioactive ☢️
Relative Atomic Mass
259.100445 ± 0.000108 Da
Mass Number259
G-Factor
Half Life
1.6 ± 0.06 h
Spin7/2
Quadrupole Moment
Discovery Year1982
Parity-

259Md Decay Modes
Decay ModeIntensity
SF (spontaneous fission)100%
α (α emission)%

260Md

AbundanceRadioactive ☢️
Relative Atomic Mass
260.10365 ± 0.000339 Da
Mass Number260
G-Factor
Half Life
27.8 ± 0.8 d
Spin
Quadrupole Moment
Discovery Year1989
Parity

260Md Decay Modes
Decay ModeIntensity
SF (spontaneous fission)100%
α (α emission)5%
ϵ (electron capture)5%
β (β decay)3.5%

261Md

AbundanceRadioactive ☢️
Relative Atomic Mass
261.105828 ± 0.000546 Da
Mass Number261
G-Factor
Half Life
Spin7/2
Quadrupole Moment
Discovery Year
Parity-

261Md Decay Modes
Decay ModeIntensity
α (α emission)%

262Md

AbundanceRadioactive ☢️
Relative Atomic Mass
262.109144 ± 0.000481 Da
Mass Number262
G-Factor
Half Life
Spin
Quadrupole Moment
Discovery Year
Parity

262Md Decay Modes
Decay ModeIntensity
SF (spontaneous fission)%
α (α emission)%

History

Mendelevium was discovered by Albert Ghiorso, Glenn T. Seaborg, Gregory R. Choppin, Bernard G. Harvey and Stanley G. Thompson in 1955 at the University of California, Berkeley. It was produced by the bombardment of einsteinium with helium. Mendelevium was identified by chemical analysis in an ion exchange experiment. Named after Dmitri Mendeleev, who created the Periodic Table

DiscoverersG.T.Seaborg, S.G.Tompson, A.Ghiorso, K.Street Jr.
Discovery LocationUnited States
Discovery Year1955
Etymology (Name Origin)Named in honor of the scientist Dmitri Ivanovitch Mendeleyev, who devised the periodic table.
Pronunciationmen-deh-LEE-vi-em (English)
Mendelevium is harmful due to its radioactivity
Mendelevium was the first element to be produced one atom at a time

Uses

Mendelevium is used for scientific research purposes only. It has no significant commercial applications.

Sources

Made by bombarding einsteinium with helium ions.

Abundance
Abundance in Earth's crust
Abundance in Oceans
Abundance in Human Body
0 %
Abundance in Meteor
0 %
Abundance in Sun
0 %
Abundance in Universe
0 %

Nuclear Screening Constants