101
  Md  
258.000000
Mendelevium

Name: Mendelevium
Symbol: Md
Atomic Number: 101
Atomic Weight: 258.000000
Family: Rare Earth Elements
CAS RN: 7440-11-1
Description: A radioactive rare earth metal.
State (25 ° C): Solid
Oxidation states: +2,+3

Molar Volume: unknown
Valence Electrons: 5f137s2

Boiling Point: unknown
Melting Point: 1100oK, 827oC, 1521oF
Elec. Energy Level: 2, 8, 18, 32, 31, 2
Isotopes: 18 + None Stabel +1 meta state
Heat of Vaporization: unknown
Heat of Fusion: unknown
Density:  unknown
Specific Heat: unknown
Atomic Radius: unknown
Ionic Radius: unknown
Electronegativity: 1.3 (Pauling), 1.2 (Allrod Rochow)
89
Ac
227.0
90
Th
232.0
91
Pa
231.0
92
U
238.0
93
Np
237.0
94
Pu
(244)
95
Am
(243)
96
Cm
(247)
97
Bk
(247)
98
Cf
(251)
99
Es
(252)
100
Fm
(257)
101
Md
(258)
102
No
(259)
103
Lr
(260)

1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d10f13 6s2p6 7s2

History

Mendelevium (for Dmitri Mendeleyev, surname commonly spelt as Mendeleev, Mendeléef, or even Mendelejeff, and first name sometimes spelt as Dmitry or Dmitriy) was first synthesized by Albert Ghiorso (team leader), Glenn T. Seaborg, Bernard G. Harvey, Gregory R. Choppin, and Stanley G. Thompson in early 1955 at the University of California, Berkeley.  They bombarded the isotope 253Es with helium ions (alpha particles) in the Berkeley 60-inch cyclotron, ejecting a neutron and yileding a nucleus of 256Md.   256Md has a half-life of 78 minutes. This first identification was notable in that 256Md was synthesized on a one-atom-at-a-time basis.  The most stable isotope is 258Md with a half-life of 51.5 days.

dmendeleev.jpg (14975 bytes)

Dimitri Mendeleev

Characteristics

Researchers have shown that mendelevium has a moderately stable dipositive (II) oxidation state in addition to the more characteristic (for actinide elements) tripositive (III) oxidation state.  256Md has been used to find out some of the chemical properties of this element while in an aqueous solution.  There are no other uses of mendelevium and only trace amounts of the element have ever been produced.

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d10 4f14
5s2 5p6 5d10 5f13
6s2 6p6
7s2

Applications

Since only small amounts of mendelevium have ever been produced, it currently has no uses outside of basic scientific research.

Isotopes

Eighteen radioisotopes of mendelevium have been characterized, with the most stable being 258Md.   258Md produced by the bombardment of an isotope of einsteinium with ions of helium has a half-life of 51.5 days.  It decays into 254Es through alpha decay or decays through spontaneous fission.   260Md has a half-life of 31.8 days and 257Md a half-life of 5.52 hours.   All of the remaining radioactive isotopes have half-lifes that are less than 97 minutes, and the majority of these have half-lifes that are less than 5 minutes. This element also has 1 meta state258mMd (t½ 57 minutes). The isotopes of mendelevium range in atomic weight from 245.08083 amu (245Md) to 262.10887 amu (262Md).  Eventually enough 258Md should be made to determine its physical properties.

atom.gif (700 bytes)

Isotope  
Atomic Mass
 
Half-Life
245Md 245.08083 0.90 ms
246Md 246.08189 1.0 seconds
247Md 247.08164 1.12 seconds
248Md 248.08282 7 seconds
249Md 249.08301 24 seconds
250Md 250.08442 52 seconds
251Md 251.08484 4.0 minutes
252Md 252.08656 2.3) minutes
253Md 253.08728 12 minutes
254Md 254.08966 10 minutes
255Md 255.091083 27 minutes
256Md 256.09406 77 minutes
257Md 257.095541 5.52 hours
258Md 258.098431 51.5 days
258mMd   57.0 minutes
259Md 259.10051 1.60 hours
260Md 260.10365 31.8 days
261Md 261.10572 ~40 minutes
262Md 262.10887 ~3 minutes

Mendeleyev's 1872 Periodic Table

atom.gif (700 bytes)

Mendeleev.gif (28720 bytes)

atom.gif (700 bytes)

Mendelevium Data

 

Atomic Structure

Atomic Radius (Å): unknown
Atomic Volume: unknown
Covalent Radius: unknown
Crystal Structure: unknown
Ionic Radius: unknown

Chemical Properties

Electrochemical Equivalent: 3.21g/amp-hr
Electron Work Function: unknown
Electronegativity: 1.3 (Pauling); 1.2 (Allrod Rochow)
Heat of Fusion: unknown
First Ionization Potential: 6.58
Second Ionization Potential: unknown
Third Ionization Potential: unknown
Valence Electron Potential (-eV): unknown
Ionization Energy (eV): 6.58 eV

Physical Properties

Atomic Mass Average: 258
Boiling Point: unknown
Melting Point: 1100oK, 827oC, 1521oF
Heat of Vaporization: unknown
Coefficient of Lineal Thermal Expansion/K-1:
Electrical Conductivity: unknown
Thermal Conductivity: 0.1 W/cmK
Density: unknown
Enthalpy of Atomization: unknown
Enthalpy of Fusion: unknown
Enthalpy of Vaporization: unknown
Molar Volume: unknown
Specific Heat: unknown
Vapor Pressure: unknown
Estimated Crustal Abundance: unknown
Estimated Oceanic Abundance: unknown