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About Mendelevium

Mendelevium Bohr

Mendelevium, a radioactive transuranic actinide, was the first element to be synthesized one atom at a time and the ninth transuranic element to be synthesized. The painstaking task, completed by a team at the University of California Berkely in 1955, produced a total of only seventeen atoms. The synthesis required bombarding einsteinium-253, itself a synthetic element that requires significant effort to prepare and isolate in appreciable quantities, with alpha particles in the Berkeley lab's cyclotron. Following the synthesis, the seventeen atoms of the new element were purified using ion-exchange chromatography. The element's discovery, as well as its naming after the father of the modern periodic table, Dimitri Mendeleev, were accepted by the IUPAC later in 1955.

One of the superheavy elements, mendelevium is very unstable, with the most stable isotope having a half-life of about 55 days, and the originally synthesized isotope, mendelevium-56, having a half-life of only 87 minutes. Mendelevium has no commercial applications, but remains of interest to science researchers.

Mendelevium Properties

Mendelevium Bohr ModelMendelevium is a Block F, Group 3, Period 7 element. The number of electrons in each of mendelevium's shells is 2, 8, 18, 32, 31, 8, 2 and its electronic configuration is [Rn] 5f13 7s2. The mendelevium atom has a Van der Waals radius of In its elemental form, mendelevium's CAS number is 7440-11-1. Mendelevium is radioactive and therefore considered harmful. Mendelevium was discovered by Albert Ghiorso, Bernard G. Harvey, Gregory R. Choppin, Stanley G. Thompson and Glenn T. Seaborg at the Lawrence Berkeley National Laboratory in 1955. Mendelevium was named after Russian chemist Dmitri Ivanovitch Mendeleyev, who created the periodic table. Mendelevium is a synthetic element that is usually produced by bombarding einsteinium with alpha particles. Mendelevium was the ninth transuranic element of the actinide series to be discovered.

Mendelevium information, including technical data, properties, and other useful facts are discussed below. Scientific facts such as the atomic structure, ionization energy, abundance on Earth, conductivity and thermal properties are included.

Symbol: Md
Atomic Number: 101
Atomic Weight: 258
Element Category: Actinide
Group, Period, Block: n/a, 7, f
Color: unknown (presumably metallic/ silvery white/ gray)
Other Names: Mendelevio
Melting Point: 827°C, 1520.6°F, 1100.15 K
Boiling Point: N/A
Density: N/A
Liquid Density @ Melting Point: N/A
Density @ 20°C: N/A
Density of Solid: N/A
Specific Heat: N/A
Superconductivity Temperature: N/A
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): N/A
Heat of Vaporization (kJ·mol-1): N/A
Heat of Atomization (kJ·mol-1): 116
Thermal Conductivity: N/A
Thermal Expansion: N/A
Electrical Resistivity: N/A
Tensile Strength: N/A
Molar Heat Capacity: N/A
Young's Modulus: N/A
Shear Modulus: N/A
Bulk Modulus: N/A
Poisson Ratio: N/A
Mohs Hardness: N/A
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: N/A
Pauling Electronegativity: 1.3
Sanderson Electronegativity: N/A
Allred Rochow Electronegativity: 1.2
Mulliken-Jaffe Electronegativity: N/A
Allen Electronegativity: N/A
Pauling Electropositivity: 2.7
Reflectivity (%): N/A
Refractive Index: N/A
Electrons: 101
Protons: 101
Neutrons: 157
Electron Configuration: [Rn] 5f137s2
Atomic Radius: N/A
Atomic Radius,
non-bonded (Å):
Covalent Radius: N/A
Covalent Radius (Å): 1.73
Van der Waals Radius: 246 pm
Oxidation States: 2, 3
Phase: (predicted)
Crystal Structure: N/A
Magnetic Ordering: N/A
Electron Affinity (kJ·mol-1) Unknown
1st Ionization Energy: 635 kJ·mol-1 (estimated)
2nd Ionization Energy: N/A
3rd Ionization Energy: N/A
CAS Number: 7440-11-1
EC Number: N/A
MDL Number: N/A
Beilstein Number: N/A
SMILES Identifier: [Md]
InChI Identifier: InChI=1S/Md
PubChem CID: 23943
ChemSpider ID: 22385
Earth - Total: N/A
Mercury - Total: N/A
Venus - Total: N/A
Earth - Seawater (Oceans), ppb by weight: N/A
Earth - Seawater (Oceans), ppb by atoms: N/A
Earth -  Crust (Crustal Rocks), ppb by weight: N/A
Earth -  Crust (Crustal Rocks), ppb by atoms: N/A
Sun - Total, ppb by weight: N/A
Sun - Total, ppb by atoms: N/A
Stream, ppb by weight: N/A
Stream, ppb by atoms: N/A
Meterorite (Carbonaceous), ppb by weight: N/A
Meterorite (Carbonaceous), ppb by atoms: N/A
Typical Human Body, ppb by weight: N/A
Typical Human Body, ppb by atom: N/A
Universe, ppb by weight: N/A
Universe, ppb by atom: N/A
Discovered By: Lawrence Berkeley Nat'l Laboratory
Discovery Date: 1955
First Isolation: N/A

Mendelevium Isotopes

Mendelevium is an artificial element. It has no stable isotopes.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
245Md 245.08081(33)# 0.90(25) ms SF (1/2-)# N/A 1822.989014 -
246Md 246.08171(28)# 1.0(4) s a to 242Es; ß+  to 246Fm N/A N/A 1830.208008 -
247Md 247.08152(22)# 1.12(22) s SF 1/2-# N/A 1838.399048 -
248Md 248.08282(26)# 7(3) s ß+  to 248Fm; a to 244Es; SF N/A N/A 1845.44104 -
249Md 249.08291(22)# 24(4) s a to 243Es; ß+  to 247Fm (7/2-) N/A 1853.426025 -
250Md 250.08442(32)# 52(6) s ß+  to 250Fm; a to 246Es; SF N/A N/A 1860.113037 -
251Md 251.084774(20) 4.0(5) min ß+  to 251Fm; a to 247Es 7/2-# N/A 1867.782959 -
252Md 252.08643(14)# 2.3(8) min ß+  to 252Fm; a to 248Es N/A N/A 1874.26001 -
253Md 253.08714(3)# 12(8) min [6(+12-3) min] ß+  to 253Fm; a to 249Es 7/2-# N/A 1881.725952 -
254Md 254.08959(11)# 10(3) min ß+  to 254Fm; a to 250Es (0-) N/A 1887.52002 -
255Md 255.091084(7) 27(2) min ß+  to 255Fm; a to 251Es; SF (7/2-) N/A 1894.333618 -
256Md 256.09389(13)# 77(2) min ß+  to 256Fm; a to 252Es (1-) N/A 1899.631348 -
257Md 257.0955424(29) 5.52(5) h a to 253Es; EC to 257Fm; SF (7/2-) N/A 1906.322388 -
258Md 258.098431(5) 51.5(3) d EC to 258Fm (8-)# N/A 1911.70105 -
259Md 259.10051(22)# 1.60(6) h a to 255Es; SF 7/2-# N/A 1917.837036 -
260Md 260.10365(34)# 27.8(8) d EC to 260Fm; a to 256Es; ß- to 260No N/A N/A 1922.980957 -
261Md 261.10583(62)# 40# min a to 257Es 7/2-# N/A N/A -
262Md 262.10910(45)# 3# min SF N/A N/A N/A -