Mendelevium (101)

Mendelevium is a synthetic element with the symbol Md (formerly Mv) and the atomic number 101. A metallic radioactive transuranic element in the actinide series, mendelevium is usually synthesized by bombarding einsteinium with alpha particles. It was named after Dmitri Ivanovich Mendeleev, who created the periodic table, the standard way to classify all the chemical elements

Name: Mendelevium Symbol: Md Atomic number: 101 Atomic weight: [ 258 ] Standard state: presumably a solid at 298 K CAS Registry ID: 7440-11-1

Group in periodic table: Group name: Actinoid Period in periodic table: 7 (actinoid) Block in periodic table: f-block Colour: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic

Historical information

Mendelevium was discovered by Glenn T. Seaborg, Albert Ghiorso, Bernard Harvey, Gregory Choppin, Stanley G. Thompson at 1955 in USA. This element was named after Dimitri "Mendeleev", the Russian chemist who contributed so much to the development of the periodic table.

Mendelevium, the ninth transuranium element of the actinide series to be discovered, was first identified by Seaborg and others in 1955 as a product of the bombardment of the einsteinium isotope ²⁵³Es with alpha particles (helium nuclei) in the Berkeley Radiation Laboratory's 60-inch cyclotron (²⁵⁶Md was the first isotope of any element to be synthesized one atom at a time). The isotope produced was ²⁵⁶Md, which has a half-life of about 1¹/₄ hours. Mendelevium was the ninth transuranic element synthesized. The first 17 atoms of this element were created and analyzed using the ion-exchange adsorption-elution method. During the process, mendelevium behaved very much like thulium (# 69), its naturally occurring homologue

Physical properties

• Melting point: about 1100 [or 827 °C (1521 °F)] K

Mendelevium: orbital properties

• Ground state electron configuration:  [Rn].5f¹³.7s²
• Shell structure:  2.8.18.32.31.8.2
• Term symbol:   ²F_7/2
• Pauling electronegativity: 1.3 (Pauling units)
• First ionization energy: 635 kJ mol^-1