Category Chemistry

Making mendelevium, one atom at a time?

The discovery of mendelevium was announced at the end of April in 1955. It was described by one of its discoverers as “one of the most dramatic in the sequence of syntheses of transuranium elements”.

The search for new elements is something that scientists have been doing for hundreds of years. Once Russian chemist Dmitri Mendeleev organised the elements known at his time according to a repeating, or periodic (and hence the name periodic table), system in the 1860s, the search became a little easier.

This was because the gaps in Mendeleev’s periodic table pointed to elements that weren’t known yet. The properties of these elements, however, could be predicted based on their place in the table and the neighbours around them, thereby making it easier to discover new elements. Mendeleev’s table has since been expanded, to make space for other new elements

One of those new elements discovered was element number 101, named mendelevium after. Mendeleev. American Nobel Prize winner Glenn Seaborg, who was one of the discoverers of the element, wrote that the discovery of mendelevium was “one of the most dramatic in the sequence of syntheses of transuranium elements”, in a chapter co-written by him for The New Chemistry. Additionally, he also wrote in that chapter that “It was the first case in which a new element was produced and identified one atom at a time.”

Begins with a bang                                                                       

Ivy Mike, the first thermonuclear device, was dropped for testing on the Eniwetok Atoll in the Pacific Ocean in 1952, sending a radioactive cloud into the air, from which samples were collected. The lab reports suggested that two new elements-elements 99 (einsteinium) and 100 (fermium) – were discovered from the debris. The discoveries came at a time when there was a race to discover new elements.

 The leading researchers of the U.S. involved in this race were camped at the Radiation Laboratory at the University of California, Berkeley, under the direction of physicist Ernest Lawrence A team of scientists which included Albert Ghiorso, Stanley Thompson, Bernard Harvey, Gregory Choppin, and Seaborg, came up with a plan to produce element 101 using a billion atoms of einsteinium-253 that were formed in a reactor.

The idea was to spread the atoms of einsteinium onto a thin gold foil. As its half-life was about three weeks, the researchers effectively had a week to perform their experiments after receiving it. Based on Ghiorso’s calculations, they were aware that only about one atom of the new element 101 would be produced for every three hours the gold foil was bombarded with alpha particles.

Race against time

As the experiment would yield only a very small amount of the new element, the scientists set up a second gold foil behind the first to catch the atoms. It was a race against time as well as the half-life of element 101 was expected to be a few hours only.

With the Radiation Laboratory atop a hill and the cyclotron at its base, there really was a mad rush to get the samples to the lab on time. The samples “were collected in a test tube, which I took and then jumped in a car driven by Ghiorso”, is how Choppin put it in his own words.

On the night of the discovery, the target was irradiated in three-hour intervals for a total of nine hours. By 4 AM on February 19, 1955, they had recorded five decay events characteristic of element 101 and eight from element 100, fermium. With conclusive evidence of element 101’s existence, Choppin mentions that “We left Seaborg a note on the successful identification of Z =101 and went home to sleep on our success.”

At the end of April 1955, the discovery of element 101 was announced to the world. The university’s press release stated that “The atoms of the new element may have been the rarest units of matter that have existed on earth for nearly 5 billion years… The 17 atoms of the new element all decayed, of course, and the ‘new’ element is for the present extinct once again.”

Cold War era

As element 101 marked the beginning of the second hundred elements of the periodic table, the scientists wanted to name it after Mendeleev, the man behind the periodic table.

Despite the discovery happening during the Cold War era, Seaborg was able to pull enough strings to convince the U.S. government to accept the proposal to name the element after a Russian scientist. The International Union of Pure & Applied Chemistry approved the name mendelevium and the scientists published their discovery in the June 1955 issue of Physical Review Letters.

While only small quantities of mendelevium have ever been produced, more stable isotopes of the element have since been made. The most stable version known as of now has a half-life of over one-and-a-half months, allowing for better opportunities to further study heavy elements and their properties.

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Is glass a solid or an exceptionally slow-moving liquid?

Artists have worked wonders with glass ever since its discovery. A look at glass art…

Is glass a solid or an exceptionally slow-moving liquid? While scientists have not been able to figure that out, artists have worked wonders with glass ever since it was discovered in 3500 BC in Mesopotamia. Glass is an incredibly versatile substance to work with. Its ability to withstand extreme temperatures, resistance to chemical reactions and transparency make it ideal for use as vessels and window panes and also enables artists to give free rein to their creativity as they fashion beautiful objets d'art.

Artworks created from glass can be categorised into three types:

Glass art – large modem glass sculptures, usually displayed in public spaces. For example. "The Sun" created by American glass sculptor Dale Chihuly.

Art glass – small decorative pieces, designed especially for display at home (not for daily use) such as crystal ware from reputed brands.

Studio glass – sculptures or three-dimensional artworks. These include beautiful works of art like stained glass and Murano glass.

Gothic churches of Europe take pride in their lustrous stained glass windows. Each window was carefully crafted by piecing together small bits of coloured glass to form an intricate mosaic, be it a biblical scene or simply a geometric pattern. The glass pieces were held in place by soldered metal strips. The rose windows of Notre Dame Cathedral in Paris are spectacular examples of this art form.

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What do we know about the platinum group of metals?

A group of six metals – ruthenium, rhodium, palladium, osmium, iridium, and platinum-are known as the platinum group of metals or PGM. The group is called by this name because platinum is found more than the others though all of them are very rare.

The platinum groups of metals have physical, chemical and anatomical similarities. They are dense, stable and are often recycled to have longer lives. The group has a variety of highly specialized uses.

Platinum is a silvery white metal that is more expensive than gold. It is used to make jewellery. Platinum and palladium are often used as catalysts. Iridium and rhodium are harder and have a lot of alloying applications. There are very few minerals containing the platinum group of metals, and they are found mainly in South Africa and Russia.

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Why is radium not widely used now?

No one knew of the dangers radium posed when it was produced for the first time. Radium had an aura of mystery which attracted people. Moreover, people were fascinated by how it glowed when mixed with phosphor. No wonder, industries sprang up to manufacture hundreds of consumer products containing radium.

The health hazard caused by this fascinating new element was identified only later. The harmful effects of radium such as skin burns and hair loss were observed among early experimenters. Many of them died as a result of their work.

The widespread use of radium was later halted for health and safety reasons. But, its wide use in luminescent paints continued through World War II. The soft glow of radium’s luminescence made aircraft dials, gauges and other instruments visible to their operators at night.

Radium was also an early radiation source for cancer treatment. Small radioactive seeds were implanted in tumours to kill cancerous cells. Safer and more effective radiation sources are used today.

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What do we know about the discovery of radium?

The discovery of radium is one of the most interesting stories in science. The story begins with the research of the French physicist Antoine-Henri Becquerel of the ore called pitchblende containing the element uranium. Becquerel found that pitchblende gives off radiation.

Becquerel’s discovery caused great excitement among scientists. Many physicists stopped their own research and began to study this novelty. A scientist couple Marie and Pierre Curie were especially interested in pitchblende.

Eventually, they isolated a new element that gave off more intense radiation than pitchblende itself. The Curies named this new element polonium. That was not the end. They believed that there would be at least one other element in the pitchblende.

The couple continued with their studies and in 1898, they isolated a second new element- radium. Radium gave away intense radiations and it took the Curies another four years to prepare one gram of the element. To do so, they had to sift through more than seven metric tons of pitchblende!

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Is strontium dangerous?

Strontium is a silvery metal that rapidly turns yellowish in air. It is found as a free metal in nature and is not dangerous. This is because the naturally occurring strontium is not radioactive. But strontium has some isotopes that are highly unstable and potentially dangerous. Strontium-90 is one such isotope of strontium.

Strontium-90 is produced as a result of a nuclear reaction. It became famous in the 1960s when it was produced as the result of an atomic bomb testing. In fact, when a nuclear explosion takes place, the tens of millions of tons of earth and rock that are thrown skywards contain strontium-90.

Strontium-90 contaminates air, water, soil and vegetation; severe radiations produced in the process can sicken both animals and humans and can even result in deaths.

Strontium-90 affects human bone tissues, marrow and blood. It can cause leukaemia and bone cancer too.

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