Mendelevium

Chaitra 26/06/2026 19:58:09 Updated 26/06/2026 19:58:09

Property	Value
Atomic Number	101
Element	Mendelevium
Symbol	Md
Atomic Mass	[258] (most stable isotope)
Number of Neutrons	157 (Mendelevium-258)
Number of Protons	101
Number of Electrons	101
Period	7
Group	Actinide (no fixed group number)
Phase	Solid (predicted)
Radioactive	Yes
Natural	No (synthetic element)
Metal	Yes
Nonmetal	No
Metalloid	No
Type	Actinide
Atomic Radius	~190 pm (estimated)
Electronegativity	1.30 (estimated)
First Ionization Energy	6.58 eV (estimated)
Density	~10.3 g/cm³ (estimated)
Melting Point	827 °C (estimated)
Boiling Point	— (not well established)
Number of Isotopes	No stable isotopes (Md-258 most notable)
Discoverer	Albert Ghiorso, Glenn T. Seaborg, Gregory R. Choppin, Bernard G. Harvey, Stanley G. Thompson
Year	1955
Specific Heat	— (not well established)
Number of Shells	7
Number of Valence Electrons	3