- Nobelium (No) is a synthetic, radioactive metal with atomic number 102, belonging to the actinide series.
- Its electron configuration is [Rn] 5f¹⁴ 7s², and it typically exhibits the +2 oxidation state in aqueous solution, although the +3 state is also possible. This unusual preference for the +2 state distinguishes nobelium from most other actinides, which generally favor +3.
- The atomic structure contains one hundred and two protons, most often one hundred and fifty-seven neutrons in nobelium-259 (²⁵⁹No), and one hundred and two electrons arranged in seven shells.
- Nobelium does not occur naturally and is produced in particle accelerators by bombarding lighter actinides such as curium or californium with carbon or nitrogen ions. The most stable isotope is nobelium-259 (²⁵⁹No), with a half-life of about 58 minutes, though most other isotopes have half-lives of only seconds.
- The discovery of nobelium was surrounded by controversy. In 1957, a Swedish team at the Nobel Institute for Physics in Stockholm reported its discovery after bombarding curium-244 with carbon ions, but their results were later shown to be incorrect. In 1958, a joint team of Soviet scientists at the Joint Institute for Nuclear Research in Dubna announced the creation of nobelium, claiming the synthesis of isotopes ²⁵²No and ²⁵⁴No, though their findings were also questioned. Finally, in 1966, a team at the Lawrence Berkeley National Laboratory in California, led by Albert Ghiorso, produced conclusive evidence for the element by bombarding curium-248 (²⁴⁸Cm) with carbon-12 ions, confirming the existence of nobelium isotopes. The element was officially named nobelium in honor of Alfred Nobel, the inventor of dynamite and founder of the Nobel Prizes.
- Because nobelium can only be produced atom by atom and decays rapidly, it has no practical applications outside of basic scientific research. Its study is significant for advancing knowledge about the chemical behavior of the heaviest actinides and for testing predictions about electron configurations in superheavy elements.
- Chemically, nobelium is unique among the actinides in that the +2 oxidation state (No²⁺) is more stable than the +3 state in aqueous solution. Compounds such as nobelium(II) chloride (NoCl₂) and nobelium(II) nitrate (No(NO₃)₂) can be formed, while nobelium(III) compounds are less stable under normal conditions. This property gives it greater resemblance to the alkaline earth metals, particularly radium, than to its actinide neighbors.
- Biologically, nobelium has no role and is highly radiotoxic due to its alpha radiation. Because of its scarcity and short half-life, it poses little direct biological or environmental risk.
- Environmentally, nobelium is an artificial element that exists only in nuclear research laboratories. It does not occur in nature and decays too quickly to accumulate in any significant quantity.
