Introduction to Fermium
Fermium (Fm), atomic number 100, is a synthetic element, meaning it does not occur naturally on Earth and must be produced in laboratories or nuclear reactions. It belongs to the actinide series on the periodic table, a group of metallic elements characterized by their high atomic numbers and radioactivity.
Discovery and Properties
Fermium was first identified in the aftermath of the “Ivy Mike” thermonuclear test in 1952, conducted by the United States. Scientists at the University of California, Berkeley, led by Albert Ghiorso, analyzed debris from the explosion and discovered isotopes of elements 99 and 100, which were later named Einsteinium and Fermium, respectively. This discovery highlighted the extreme conditions under which new elements could be formed through intense neutron bombardment. Only minute quantities of fermium have ever been produced, typically in picogram (trillionths of a gram) amounts, making extensive study of its properties challenging.
Chemical Reactivity
The chemical reactivity of fermium is largely predicted based on trends observed in lighter actinide elements, as macroscopic quantities sufficient for direct experimentation are unavailable. All known isotopes of fermium are highly radioactive, with the longest-lived isotope, Fermium-257, possessing a half-life of approximately 100.5 days. The extremely short half-lives of most fermium isotopes severely limit the time available for chemical study.
General Reactivity Trends
Based on its position in the actinide series, fermium is expected to behave as a reactive metal. Actinides typically exhibit a stable +3 oxidation state in aqueous solutions, and radiochemical studies have confirmed that fermium also readily forms the Fm$^{3+}$ ion. This characteristic behavior is crucial for its separation and identification from other elements.
Interaction with Water
If macroscopic quantities were available, fermium would be expected to react with water, similar to other reactive metals in the actinide series. This reaction would likely produce fermium hydroxide and release hydrogen gas, particularly when heated. However, direct experimental observation of fermium reacting with water has not been conducted due to the element’s scarcity and radioactivity.
Interaction with Air
Reactive metals generally tarnish or oxidize upon exposure to air (specifically oxygen). Fermium is predicted to be susceptible to oxidation by atmospheric oxygen, forming fermium oxides. The specific conditions required for this reaction and the exact composition of the oxide are not known through direct observation but are inferred from the behavior of its actinide neighbors.
Safety and Characteristic Features
Radioactivity
All isotopes of fermium are highly radioactive. They undergo alpha decay, emitting high-energy alpha particles. This high level of radioactivity means that even minuscule amounts pose significant health risks if handled improperly or if they enter the body. Strict containment and shielding protocols are required when working with any fermium isotopes in research facilities.
Toxicity
Due to its intense radioactivity, fermium is considered highly toxic. If ingested, inhaled, or absorbed through the skin, the emitted alpha particles can cause severe damage to biological tissues and DNA, increasing the risk of cancer and other radiation-induced illnesses. Like other heavy radioactive elements, if it were to accumulate in the skeleton, it would pose a continuous internal radiation hazard.
Flammability
While no specific flammability data exists for fermium, many reactive metals, especially when in a finely divided powder form, are pyrophoric, meaning they can ignite spontaneously in air. Given fermium’s predicted metallic nature and reactivity, a similar characteristic is plausible if it could be produced in such a form, though this remains purely theoretical due to the element’s extreme scarcity.
Studying Fermium’s Chemistry
One of the most notable “chemical reactions” involving fermium is not a macroscopic process but rather the radiochemical separation and identification that led to its discovery and confirmed its chemical properties. Following the “Ivy Mike” nuclear test, scientists performed intricate chemical separations on the bomb debris. They used techniques like ion-exchange chromatography to separate the newly formed elements from other fission products and transuranic elements. By observing how fermium isotopes behaved on these columns – for example, their elution order – scientists confirmed its expected place as an actinide, showing it formed a +3 ion and behaved chemically similarly to lighter actinides like einsteinium and californium. This process of chemical isolation and characterization, relying on the predictable behavior of elements in solution, served as the primary method to understand its chemistry.