Einsteinium

Einsteinium is a special kind of material that scientists create in laboratories. It is not found in nature and has the symbol Es and atomic number 99. Einsteinium belongs to a group called the actinides and is one of the elements made after uranium.

Einsteinium was first found in 1952 after the explosion of the first hydrogen bomb. The most common form of einsteinium, called einsteinium-253, is made in special powerful nuclear reactors. Only tiny amounts are produced, about one milligram each year, and it is very hard to separate from other materials. Because there is so little of it and it does not last long, einsteinium is mostly used for basic science experiments. For example, it helped scientists make a new element called mendelevium in 1955.

Einsteinium looks like a soft, shiny metal and glows because it is very radioactive. It is hard to study because it changes quickly into other elements. It is also very dangerous if it is swallowed, as it can harm the body because of its radioactivity.

History

Einsteinium was first found in December 1952 by Albert Ghiorso and his team at the University of California, Berkeley. They discovered it in the fallout from the Ivy Mike nuclear test on November 1, 1952, at Enewetak Atoll in the Pacific Ocean. This was the first successful test of a thermonuclear weapon.

The scientists analyzed materials from the explosion and found a new isotope of plutonium, which could only have formed by capturing six neutrons from uranium-238, followed by two beta decays. This suggested that even more neutrons could be captured, creating heavier elements than californium.

Ghiorso’s team studied filter papers flown through the explosion cloud and later isolated more material from coral debris. They used special chemistry techniques to separate the new elements and detected einsteinium-253 (253Es) through its high-energy alpha decay. It was produced when uranium-238 captured 15 neutrons and then underwent seven beta decays. This process was possible due to the high neutron flux during the explosion.

Some uranium atoms captured even more neutrons, leading to einsteinium-255 (255Es) and fermium-255 (255Fm). The discovery was kept secret until 1955 due to Cold War tensions. The findings helped confirm theories about how heavy elements form in supernovas.

The Berkeley team also produced einsteinium in laboratories using nuclear reactions. They suggested naming the element after Albert Einstein and Enrico Fermi. The name einsteinium (Es) was announced at the Geneva Atomic Conference in August 1955.

Characteristics

Einsteinium is a synthetic, silvery, radioactive metal. It sits in the periodic table between the actinides californium and fermium, and below the lanthanide holmium. It has a density of 8.84 g/cm³, which is lower than californium but similar to holmium. Einsteinium also has a relatively low melting point of 860 °C.

Unlike some lighter actinides, einsteinium is believed to have a face-centered cubic structure. However, its strong radioactivity damages its crystal lattice quickly, causing it to glow. Because samples are very small and hard to study, scientists often heat the metal to observe its properties. Einsteinium is also very reactive and can exist in different chemical states, which is unusual for actinides.

The most stable isotope of einsteinium, ²⁵²Es, has a half-life of 471.7 days. All isotopes of einsteinium are radioactive and decay quickly. Because of this, einsteinium does not occur naturally and must be made in laboratories or nuclear reactors.

Synthesis and extraction

Einsteinium is made in very small amounts by using strong nuclear tools to change lighter elements. Two main places where this happens are the High Flux Isotope Reactor in Tennessee, U.S., and the SM-2 loop reactor in Russia. These reactors are special because they can make very heavy elements, but only tiny bits are produced each year.

In the past, scientists made a very small amount of einsteinium in 1961. Later, they made more, but it was still just a little bit. Making einsteinium needs special tools and careful work.

Laboratory synthesis

Scientists can make einsteinium in different ways in labs. One way is by using plutonium and very strong neutron beams. This makes several types of einsteinium. Another way is to use uranium and send special particles at it.

In 1967, scientists in Russia made a new type of einsteinium by using special tools. They used americium and carbon, or uranium and nitrogen, to create it.

Synthesis in nuclear explosions

Scientists also looked at debris from big nuclear tests to see if they could find einsteinium. These tests created very strong conditions that could make heavy elements, but it was hard to collect the material. Even though they didn’t find new elements, they did get more einsteinium than before.

Separation

Getting einsteinium from the mix of materials made during these processes is very difficult. Scientists use special steps to separate it, like using chemicals and heat. They need to separate it from other similar elements, especially berkelium, because einsteinium changes quickly into berkelium.

Preparation of the metal

To get pure einsteinium metal, scientists use strong reducing agents. One way is to use lithium to change einsteinium fluoride into metal, but this method isn’t very good because einsteinium evaporates easily. Another way is to use lanthanum metal to change einsteinium oxide into metal, which works better.

Chemical compounds

Oxides

Einsteinium(III) oxide (Es₂O₃) is made by burning einsteinium(III) nitrate. It forms clear cubic crystals, first studied from very tiny samples. There are two other crystal shapes for this oxide, and which shape forms depends on how it is made. These shapes can change on their own due to radiation or heat. The crystal shape where Es³⁺ is surrounded by six O²⁻ ions is similar to lanthanum oxide.

Halides

Einsteinium can form compounds called halides in two different states. The most stable state for all halides, from fluoride to iodide, is +3.

Einsteinium(III) fluoride (EsF₃) can be made by mixing Es(III) chloride with fluoride ions or by using special gases. Its crystal shape is like that of californium(III) fluoride, where Es³⁺ ions are surrounded by fluorine ions.

Es(III) chloride (EsCl₃) is made by heating Es(III) oxide with dry hydrogen chloride gas. It forms an orange solid with a crystal shape where einsteinium atoms are surrounded by chlorine atoms.

The less common, +2 state compounds of einsteinium are made by using hydrogen to change the +3 halides.

Einsteinium(II) chloride (EsCl₂), einsteinium(II) bromide (EsBr₂) and einsteinium(II) iodide (EsI₂) have been studied using light absorption, but their crystal shapes are not yet known.

Some compounds called oxyhalides, like EsOCl, EsOBr and EsOI, are made by mixing a trihalide with water vapor and a hydrogen halide.

Organoeinsteinium compounds

Because einsteinium is very radioactive, it might be used in medical treatments to target specific parts of the body. Scientists have made special compounds to deliver einsteinium, testing them by giving them to dogs. They also tried to make einsteinium glow using light, but the glow was too weak to detect due to the compound’s energy levels. However, einsteinium ions were seen to glow in certain solutions, showing a broad peak of light that can be excited by green light. This glow lasts only a few microseconds and is not very strong.

Applications

Einsteinium is mostly used for basic science experiments, especially to make heavier elements.

In 1955, scientists used einsteinium to create a new element called mendelevium. They aimed a beam of particles at einsteinium and succeeded in making 17 atoms of this new element.

A special type of einsteinium called <sup>254</sup>Es is helpful for making even heavier elements because it lasts longer and can be found in small amounts. Scientists tried to use it to make an element called ununennium, but they didn’t find any atoms of it.

This einsteinium isotope was also used on a moon probe to help scientists study the surface of the Moon. Its heavy mass helped the instruments work better.

Safety

Most of what we know about einsteinium's effects on health comes from studies with animals. When rats ate einsteinium, only a tiny bit, about 0.01%, entered their blood. From there, most of it went to their bones and stayed there for many years, but it would break down because of its radioactivity. Some went to the lungs and a very small amount went to the reproductive organs. About 10% was passed out of the body. The way einsteinium spreads in bones is similar to another element called plutonium.