Einsteinium, designated by the symbol Es and atomic number 99, is a synthetic element that sits far down the periodic table. Einsteinium is definitively a metal. It is a highly radioactive element that does not occur naturally on Earth, meaning it must be manufactured in specialized facilities. Its properties, while challenging to study due to its unstable nature, align with the characteristics of other heavy metallic elements.
Classification as a Metal and Expected Properties
Einsteinium is located in the seventh period of the periodic table, placing it within the Actinide series, a group of elements recognized for their metallic character. This classification as an actinide metal is fundamentally derived from its electron configuration, which ends with valence electrons in the \(7s\) orbital and partially filled \(5f\) orbitals. This electronic structure dictates its tendency to lose electrons and form positive ions, the defining feature of metallic elements.
Based on its position among its neighbors, Einsteinium is expected to be a soft, silvery, and ductile metal. Experimental studies, though conducted on extremely small samples, have determined its melting point to be approximately \(860^\circ C\) and its density to be around \(8.84 \text{ g/cm}^3\). Chemically, Einsteinium primarily exhibits an oxidation state of \(+3\) in solution, a common trait for the later actinides, though a less stable \(+2\) state has also been observed. The element is also predicted to be paramagnetic.
Discovery and Synthetic Production
The element Einsteinium was first identified in the debris from the “Ivy Mike” thermonuclear test, the first successful detonation of a hydrogen bomb, which occurred in November 1952. Scientists at the University of California, Berkeley, including Albert Ghiorso, analyzed filter paper flown through the explosion cloud to confirm the existence of element 99. The initial formation occurred when Uranium-238 atoms absorbed an unprecedented number of neutrons—up to 15—which then underwent a series of beta decay events.
The discovery was initially kept secret for several years due to Cold War security concerns, but the element was eventually named in honor of physicist Albert Einstein. It must be produced synthetically using powerful nuclear methods. Today, the element is primarily manufactured in high-flux nuclear reactors, such as the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory.
This production process involves the prolonged neutron bombardment of lighter transuranic elements, such as Plutonium or Californium, over many months. The resulting Einsteinium is then chemically separated from the target material and other byproducts through complex and exacting procedures. This manufacturing method yields only microgram to milligram quantities of the element each year, highlighting the difficulty of its creation.
Instability, Scarcity, and Research Application
Einsteinium is intensely radioactive, with all of its isotopes being unstable. The most commonly produced isotope, \(\text{Es-253}\), has a half-life of only \(20.47\) days, meaning half of any given sample decays into a different element in less than three weeks. Even the longest-lived isotope, \(\text{Es-252}\), has a half-life of about \(472\) days, which is still quite short in chemical terms.
This extreme instability results in severe handling challenges and contributes to the element’s scarcity. The intense radiation emitted by Einsteinium causes a visible glow and leads to the rapid destruction of its own crystal structure, a phenomenon known as self-irradiation damage. This rapid decay and self-destruction limit the time available for researchers to study the element and its compounds before the sample is contaminated by its decay products.
Due to these limitations, Einsteinium has no commercial or industrial applications outside of specialized scientific investigation. Its primary function is to serve as a target material for the synthesis of even heavier, more exotic elements on the periodic table. For instance, \(\text{Es-253}\) was famously used as the starting material to create Mendelevium (element 101) in 1955. Studying Einsteinium also provides physicists with insight into the behavior of the heaviest elements and the fundamental properties of actinide chemistry.