Nobelium (No)

Isotopes of Nobelium

Isotope Atomic Mass Half-life Mode of Decay Nuclear Spin
No-253 253.0907 1.70 minutes α to Fm-249;
EC to Md-253
No-254 254.0909 55 seconds α to Fm-250;
EC to Md-254; SF
No-255 255.0932 3.10 minutes α to Fm-251;
EC to Md-255
No-256 256.0943 2.90 seconds α to Fm-252; AS 0
No-257 257.0968 25 seconds α to Fm-253 7/2
No-258 258.0983 0.0012 seconds α to Fm-254; SF 0


Nobelium is a radioactive rare earth metal, first correctly identified in 1966 by physicists at the Flerov Laboratory of Nuclear Reactions in Dubna, Soviet Union, although its discovery had been announced by physicists at the Nobel Institute in Sweden in 1957. The synthesis of nobelium was then claimed in April 1958 at the University of California - Berkeley, USA, by Albert Ghiorso, Glenn T. Seaborg, John R. Walton and Torbjørn Sikkeland. It is named after the Swedish chemist Alfred Nobel, who discovered dynamite.

The appearance of this element is unknown; however, it is most likely silvery-white or gray and metallic. If sufficient amounts of nobelium were produced, it would pose a radiation hazard. Twelve radioisotopes of nobelium have been characterized, the most stable being Nobelium-259, with a half-life of 58 minutes.

Properties of Nobelium

Name Nobelium
Symbol No
Atomic number 102
Atomic weight [259]
Standard state Presumably a solid at 298 °K
CAS Registry ID 10028-14-5
Group in periodic table N/A 
Group name Actinoid
Period in periodic table 7 (Actinoid)
Block in periodic table f-block
Color Unknown, but probably metallic and silvery white or grey in appearance
Classification Metallic
Melting point About 1100 °K [or 827 °C or 1521 °F]
Boiling point No data available
Electron configuration [Rn]5f147s2