The atomic number, which represents the count of protons within an atom’s nucleus, serves as the fundamental identifier for every chemical element. When the nucleus contains exactly 100 protons, it identifies a unique, synthetic element known as Fermium (Fm). Named in honor of the physicist Enrico Fermi, this element challenges the limits of nuclear stability.
The Significance of 100 Protons
Fermium is denoted by the atomic number Z=100, placing it in the seventh period of the periodic table within the Actinide series. Actinides are a specialized group of radioactive, heavy metals. Fermium is the eighth transuranic element, defined as having an atomic number greater than 92 (Uranium). Since all of its isotopes have half-lives significantly shorter than the age of the Earth, Fermium is a synthetic element. It must be created artificially for scientific study, as it does not exist naturally on our planet today.
How Fermium Was First Created
Fermium was first identified in the debris of the “Ivy Mike” thermonuclear weapon test, the first successful detonation of a hydrogen bomb by the United States in November 1952. Scientists collected samples from the radioactive cloud to analyze the fallout material. The intense neutron flux generated by the explosion was the mechanism for Fermium’s creation.
In a process called multiple neutron capture, uranium-238 absorbed a large number of neutrons rapidly. This absorption formed heavier isotopes, which then underwent beta decay to produce elements with higher atomic numbers, including element 100. The first isotope detected was Fermium-255. Because the discovery was tied to a secret weapons program, the findings were initially classified and not published until 1955, after researchers had independently produced the element in a controlled laboratory setting.
The Basic Properties of Element 100
As a synthetic actinide, Fermium is inherently radioactive; all of its roughly 20 known isotopes are unstable. The most stable isotope is Fermium-257, which has a half-life of approximately 100.5 days. This rapid decay makes studying its chemical properties difficult, as only tracer amounts (too small to be weighed) have ever been produced.
Fermium is predicted to be a solid metal at room temperature, with an estimated melting point of 1527°C. Chemically, Fermium typically forms a trivalent ion (\(\text{Fm}^{3+}\)) in aqueous solution, characteristic of late actinides. Under highly reducing conditions, it can also exist in a divalent state (\(\text{Fm}^{2+}\)), which is unusual for an actinide in solution. Due to its intense radioactivity and scarcity, Fermium has no practical commercial uses and remains solely an object of advanced scientific research.