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Mendelevium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


              101             fermium ← mendelevium → nobelium
              Tm
             ↑
             Md
             ↓
             (Upu)

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                 Name, Symbol, Number mendelevium, Md, 101
                                                 Chemical series actinides
                                            Group, Period, Block n/a, 7, f
                                      Appearance unknown, probably silvery
                                                    white or metallic gray
                                                   Atomic mass (258) g/mol
                                    Electron configuration [Rn] 5f^13 7s^2
                                Electrons per shell 2, 8, 18, 32, 31, 8, 2
                                                       Physical properties
                                                               Phase solid
                                                     Melting point 1100  K
                                                     (827 ° C, 1521 ° F)
                                                         Atomic properties
                                     Electronegativity 1.3 (Pauling scale)
                                       Ionization energies 1st: 635 kJ/mol
                                                             Miscellaneous
                                                 Magnetic ordering no data
                                             CAS registry number 7440-11-1
                                                         Selected isotopes

   CAPTION: Main article: Isotopes of mendelevium

                                  iso   NA  half-life DM  DE ( MeV)   DP
                                 ^257Md syn 5.52 h    ε   0.406     ^257Fm
                                                      α   7.558     ^253Es
                                                      SF  -         -
                                 ^258Md syn 51.5 d    ε   1.230     ^258Fm
                                 ^260Md syn 31.8 d    SF  -         -
                                                      α   7.000     ^256Es
                                                      ε   -         ^260Fm
                                                      β^- 1.000     ^260No

                                                                References

   Mendelevium ( IPA: /ˌmɛndəˈlɛviəm/), also known as unnilunium ( IPA:
   /ˌjuːniˈluːniəm/, symbol Unu) is a synthetic element in the periodic
   table with the symbol Md (formerly Mv) and the atomic number 101. A
   metallic radioactive transuranic element of the actinides, mendelevium
   is synthesized by bombarding einsteinium with alpha particles and was
   named after Dmitri Mendeleev.

Notable 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.

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 Harvey, Greg Choppin, and
   Stanley G. Thompson in early 1955. The team produced ^256Md ( half-life
   of 76 minutes) when they bombarded an ^253Es target with alpha
   particles (helium nuclei) in the Berkeley Radiation Laboratory's
   60-inch cyclotron (^256Md was synthesized one-atom-at-a-time). Element
   101 was the ninth transuranic element synthesized.

Isotopes

   15 radioisotopes of mendelevium have been characterized, with the most
   stable being ^258Md with a half-life of 51.5 days, ^260Md with a
   half-life of 31.8 days, and ^257Md with 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 state, ^258mMd (t[½]
   57 minutes). The isotopes of mendelevium range in atomic weight from
   245.091 amu (^245Md) to 260.104 amu (^260Md).
   Retrieved from " http://en.wikipedia.org/wiki/Mendelevium"
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   with only minor checks and changes (see www.wikipedia.org for details
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