Atomic Number: 101
Atomic Mass: approximately 258.0 amu (atomic mass units)
Melting Point: 827°C (1100 K or 1521°F)
Boiling Point: Unknown
Number of Protons: 101
Number of Electrons: 101
Number of Neutrons: 157
Classification: Rare Earth Metal (Man Made)
Crystal Structure: Unknown
Density @ 293 K: Unknown
This radioactive man-made element was first produced by the team of Stanley G. Thompson, Glenn T. Seaborg, Bernard G. Harvey, Gregory R. Choppin and Albert Ghiorso in 1955. They were using the 60 inch cyclotron at the University of California campus in Berkeley, California. With this device they bombarded atoms of the element einsteinum-253 with accelerated helium ions. The product of this experiment was a few atoms of the isotope mendelevium-256 which had a half life of 77 minutes. With each atom of mendelevium-256 produced one neutron was freed.
They named the new element in honor of the Russian chemist Dmitri Mendeleyev (or Mendeleev). This scientist who is often known as the father of the periodic table of elements.
As only a few atoms of mendelevium have ever been produced very little is known about the chemistry of this element. It has also been very difficult to research its bulk properties such as density and to date only its melting point is known. It is a rare earth element of the actinide or actinoid series and is situated in the f-block and period 7 of the periodic table. The actinide series also contains a number of other man-made or trans-uranium elements. Although its appearance is unknown the element is thought to be a solid at room temperature. It would most likely have a metallic sheen and be silvery-white or gray in color.
In addition to mendelevium-256 eighteen other radioactive isotopes have been produced. Mendelevium-258 is the most stable of the isotopes with a half life of 51.5 days. Mendelevium-258 decays by alpha decay to einsteinium-254. It can also decay by spontaneous fission. The isotope with the shortest half life is mendelevium-245 at 900 microseconds; this isotope also decays by spontaneous fission. Eleven of the nineteen isotopes of mendelevium can decay by spontaneous fission.
As only a few atoms of the element have ever been produced it has no industrial uses. It is studied in laboratories to gain more scientific information on the trans-uranium rare earth elements. If ever a quantity of mendelevium was produced extreme care would be required in its handling owing to its radioactive nature and tendency toward spontaneous fission.