Mendelevium

properties
[ Rn ] 5 f 13 7 s 2
101 Md
General
Name , symbol , atomic number Mendelevium, Md, 101
Element category Actinoids
Group , period , block Ac , 7 , f
CAS number 7440-11-1
Atomic
Atomic mass 258 u
Electron configuration [ Rn ] 5 f 13 7 s 2
1. Ionization energy 6th.58 (7) eV635 kJ / mol
2. Ionization energy 12.4 (4) eV1 200kJ / mol
3. Ionization energy 24.3 (4) eV2 340 kJ / mol
4. Ionization energy 40.0 (4) eV3 860 kJ / mol
5. Ionization energy 54.1 (1.9) eV5 220 kJ / mol
Physically
Physical state firmly
Chemically
Oxidation states +2, +3
Isotopes
isotope NH t 1/2 ZA ZE (M eV ) ZP
257 Md {syn.} 5.52 h ε 0.409 257 m
α 7.558 253 it
258 billion {syn.} 51.5 d α 7.241 254 it
SF
258 m Md {syn.} 60 min ε 1.230 258 ft
259 Md {syn.} 1.60 h SF
α 7.100 255 It
260 billion {syn.} 27.8 d SF
α 7,000 256 It
ε 260 m
β - 1,000 260 No.
For other isotopes see list of isotopes
Hazard and safety information

GHS hazard labeling
no classification available
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .

Mendelevium is an exclusively artificially produced chemical element with the element symbol Md and the ordinal number 101. In the periodic table it is in the group of actinides ( 7th period , f-block ) and is also one of the transurans . Mendelevium is a radioactive metal, which, however, has not yet been represented as a metal due to the small quantities available. It was discovered in 1955 and named after the Russian chemist and inventor of the periodic table, Dmitri Mendeleev . The name was finally confirmed by the IUPAC in 1994 .

history

Dmitri Ivanovich Mendeleev

Mendelevium was first created in 1955 at the University of California at Berkeley by Stanley G. Thompson , Albert Ghiorso , Bernard G. Harvey , Gregory Choppin, and Glenn T. Seaborg . The discoverers suggested the name in honor of Mendeleev, as well as the abbreviation Mv. The IUPAC decided on the name, but with the symbol Md.

To produce it, a 253 Es target was bombarded with accelerated α-particles in a cyclotron . This creates 256 Md and one free neutron .

${\ displaystyle \ mathrm {^ {253} _ {\ 99} Es \ + \ _ {2} ^ {4} He \ \ longrightarrow \ \ _ {101} ^ {256} Md \ + \ _ {0} ^ {1} n}}$

The element was later given the systematic name Unnilunium for a time.

properties

In the periodic table , the mendelevium with atomic number 101 is in the series of actinides, its predecessor is fermium , the subsequent element is nobelium . Its analogue in the series of lanthanides is thulium .

Mendelevium is a radioactive and very short-lived metal. The most stable isotope of Mendelevium is 258 Md with a half-life of approximately 51.5 days. It breaks down to 254 Es by alpha decay . It has not yet been observed in monovalent form.

safety instructions

Classifications according to the CLP regulation are not available because they only include chemical hazard and play a completely subordinate role compared to the hazards based on radioactivity . The latter also only applies if the amount of substance involved is relevant.

literature

Commons : Mendelevium  - collection of images, videos and audio files
Wiktionary: Mendelevium  - explanations of meanings, word origins, synonyms, translations

Individual evidence

1. The values ​​of the atomic and physical properties (infobox) are, unless otherwise stated, taken from: Robert J. Silva: Fermium, Mendelevium, Nobelium, and Lawrencium , in: Lester R. Morss, Norman M. Edelstein, Jean Fuger ( Ed.): The Chemistry of the Actinide and Transactinide Elements , Springer, Dordrecht 2006; ISBN 1-4020-3555-1 , pp. 1621-1651.
2. Entry on mendelevium in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 13, 2020.
3. Entry on mendelevium at WebElements, https://www.webelements.com , accessed on June 13, 2020.
4. The hazards emanating from radioactivity do not belong to the properties to be classified according to the GHS labeling. With regard to other hazards, this element has either not yet been classified or a reliable and citable source has not yet been found.
5. ^
6. ^ A. Ghiorso, B. Harvey, G. Choppin, S. Thompson, G. Seaborg: New Element Mendelevium, Atomic Number 101 , in: Physical Review , 1955 , 98  (5), pp. 1518-1519 ( doi: 10.1103 /PhysRev.98.1518 ; limited preview in Google Book search).
7. Darleane C. Hoffman, Albert Ghiorso, Glenn Theodore Seaborg: The Transuranium People: The Inside Story , Imperial College Press, 2000, ISBN 978-1-86094-087-3 , p. 201 ( limited preview in Google Book Search) .
8. David R. Lide: CRC Handbook of Chemistry and Physics , 85th Edition, CRC Press, 2004, ISBN 978-0-8493-0485-9 , Section 4, pp. 4–10 ( limited preview in Google Book Search) . This is no longer mentioned in the 90th edition (pp. 4–12 and 4–22).
9. EK Hulet, RW Lougheed, PA Baisden, JH Landrum, JF Wild, RF Lundqvist: Non-observance of monovalent Md , in: J. Inorg. Nucl. Chem. , 1979 , 41  (12), pp. 1743-1747 ( doi: 10.1016 / 0022-1902 (79) 80116-5 ).
10. K. Samhoun, F. David, RL Hahn, GD O'Kelley, JR Tarrant, DE Hobart: Electrochemical study of mendelevium in aqueous solution: No evidence for monovalent ions , in: J. Inorg. Nucl. Chem. , 1979 , 41  (12), pp. 1749-1754 ( doi: 10.1016 / 0022-1902 (79) 80117-7 ).