Transuranium Elements

Podcast Transcript

If you take a look at the periodic table of elements, you will notice something interesting.

Go to the bottom and take a look at any element over, say, number 94. You will find a bunch of elements you have probably never heard of.

Don’t worry because most chemists probably aren’t familiar with them, either. They are not part of any chemical compounds, cannot be found in nature, and most have only existed for a fraction of a second.

Learn more about transuranium elements, what they are, and how we even know they exist on this episode of Everything Everywhere Daily.

Over the course of this podcast, I’ve done many episodes on individual elements of the Periodic Table. The episode will usually talk about its atomic configuration, how the element was discovered, and its various uses.

The transuranium elements, however, are in a category all their own. They barely exist naturally, are all highly unstable, and their very existence is due to human creation. With some minor exceptions, they don’t have any use, and for most of them, they don’t really even exist, save for a tiny fraction of a second.

I’ll start by explaining what a transuranium element is.

The heaviest naturally occurring element in nature is Uranium, with an atomic number of 92. Uranium isn’t incredibly abundant, but it isn’t hard to find in rocks in many places around the world.

Having an atomic number of 92 means that there are 92 protons in the nucleus of the atom, and the number of protons is what determines what an element is.

While each element has the same number of protons, different atoms can have different numbers of neutrons in the nucleus. Atoms with different numbers of neutrons are called isotopes.

In the case of Uranium, there are two common isotopes that are found in nature: U-238 with 146 neutrons and U-235 with 143 neutrons.

Chemically, isotopes behave the same. However, different isotopes will have different levels of stability. The more unstable an atom is, the more likely it is to undergo radioactive decay.

There are only certain isotopes of any element that are stable. With the wrong configuration of protons and neutrons, it will fall apart until the resulting configuration is stable. The statistical time it takes to fall apart is known as its half-life.

Extremely unstable atoms may have half-lives of a fraction of a second. More stable atoms like uranium can have half lives in the hundreds of millions to billions of years.

The other thing to know for the purpose of this episode is that, in general, larger atomic nuclei tend to be more unstable. That is not to say you can’t have a rare isotope of a lighter element be unstable, but you won’t usually find those in the environment.

So, that brief explanation of nuclear physics aside, going into the 1940s, there were no known elements with an atomic number higher than Uranium at 92. There was nothing found in nature that had an atomic number higher than that. There were some claims of an element 93, but there was no proof. As far as everyone knew, that might have been the heaviest element in the universe.

However, it was in 1940 that experiments with nuclear fission were conducted by a team led by Edwin McMillan and Hauge Abelson at the University of California, Berkeley, who bombarded U-238 with neutrons. This created U-239, which then decayed into a new element, number 93.

The element was dubbed Neptunium because the planet Neptune is the one after Uranus.

However, they realized that if element 93 existed, then it must also decay into element 94.

Element 94 was discovered in 1941 by a man whose name is going to appear a lot in this episode, Glenn Seaborg. Seaborg worked at Berkley, and their process was very similar to that which discovered Neptunium. I’ve previously done an entire episode on Plutonium, but the only thing I will add for this episode is that extremely trace amounts of Plutonium and Neptunium have been found naturally as the result of the decay of Uranium.

However, the amounts are so small, literally scattered atoms, that for all practical purposes, you could say that Uranium is still the heaviest natural element.

The quest to create more elements continued. In 1944, as part of the Manhattan Project, Glenn Seaborg’s team discovered element 96, Curium, named after Marie Curie, and element 95, Americium, named after the United States. Both elements were created by exposing Plutonium to either alpha radiation or neutron radiation.

Both Americium and Curium actually have very limited practical uses. Americium is used in smoke detectors as a source of ionizing radiation, and Curium is used to kick-start fission chain reactions. What little that is needed is usually a byproduct of nuclear reactors.

This technique of exposing heavy elements to radiation continued to bear fruit in discovering new elements.

Seaborg’s team discovered element 97 in 1949, Berkelium. This was created by exposing Americium to alpha radiation, and element 98, Californium, was created by exposing Cuirum to alpha radiation.

Berkelium has no known use, and Californium can be used in small amounts to start nuclear chain reactions because it is a strong neutron emitter.

In 1951, Glenn Seaborg was awarded the Nobel Prize in Physics for his discovery of Transuranium elements.

However, this was nowhere near the end of the creation of elements with ever-larger atomic numbers.

In 1952, researchers at Berkley went through radioactive debris from hydrogen bomb tests on Bikini Atoll. They discovered over 200 atoms of element 99, which was dubbed Einsteinium, named after Albert Einstein.

The next year, debris from a detonation on the Enewetak atoll showed evidence of element 100, which was dubbed Fermium, after the nuclear pioneer, Enrico Fermi.

These two elements can be created in a nuclear reactor, but the higher up you go, the more difficult it becomes by an order of magnitude or more along each step in the chain.

It takes 10 grams of Curium to make one picogram of fermium. A picogram is one trillionth of a gram.

All of these heavier elements are very radioactive with very short half-lives. It is entirely possible that these elements could be created in a supernova, but they wouldn’t survive very long because of their short half-lives.

In 1955, element 101, Mendelevium, was discovered, which was created by bombarding einsteinium with alpha radiation. This was also created by Glenn Seaborg and his team.

By this time, simply exposing heavy elements to radiation had reached a dead end.

A new technique was developed, which was slamming transuranium elements with much larger atomic nuclei than just Helium, which is what alpha radiation is.

In 1961, the team at Berkley discovered element 103, Lawrencium, by bombarding californium with boron atoms.

Pretty much every discovery of a new transuranium element at this point had been made at the University of California Berkley.

The next discovery was the first outside of the United States.

In 1965, the Joint Institute for Nuclear Research in Dubna, outside of Moscow, discovered element 102, Nobelium, by bombarding Uranium with Neon atoms. This was named after Alfred Nobel, founder of the Nobel Prize

In 1969, the Soviets created element 104, Rutherfordium, created by bombarding Californium with Carbon atoms and also by bombarding Plutonium with Neon atoms. This was named after Ernst Rutherford, who discovered the atomic nucleus.

I should note that at this point, the elements being created are in extremely small numbers, and they are all incredibly radioactive with very short half-lives. The first isotope of Rutherfordium created had a half-life of five seconds

This technique of bombarding atoms with other atoms to create new elements is the technique that is still used today.

The Soviets created element 105, Dubnium, in 1970, named after the city where their research center was located in Russia.

Berkeley created element 106 in 1974, called Seaborgium, in honor of Glenn Seaborg.

After this, the next several new elements were created by researchers at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany.

In 1981, they created element 107, Bohrium, named after Niels Bohr.

In 1982, they created element 109, Meitnerium, named after Lise Meitner, one of the discoverers of atomic fission

In 1984, they made element 108, Hassium, named after the German state of Hesse.

A decade later, in 1994, they created element 110, Darmstadtium, after the city of Darmstadt, Germany, and element 111, Roentgenium, named after Wilhelm Röntgen, the discoverer of X-Rays.

In 1996, they created element 112, Copernicium, named after the astronomer Copernicus.

After almost 20 years of new element discoveries, the crown returned to Russia and the Joint Institute for Nuclear Research.

In 1999, they discovered element 114, Flerovium, named after physicist Georgy Flyorov.

In 2000, they discovered element 116, Livermorium, named after Lawrence Livermore National Laboratory in California.

In 2002, they created element 118 Oganesson, after Yuri Oganessian, the Russian counterpart of Glenn Seaborg.

You will note that the elements they discovered are not in order of atomic number.

Element 115 was created in 2003 and dubbed Moscovium after Moscow.

Element 113 was independently discovered by the Russians and a team in Japan and was named Nihonium, after the Japanese name for Japan.

Finally, in 2009, the Russians created element 117, which was dubbed Tennessine, after the state of Tennessee, the home of Oak Ridge National Laboratory.

That is all that has been discovered as of this recording. There are periodic tables out there with placeholders for the undiscovered elements 119 to 168.

So, having read off this list of elements that literally no one would bother memorizing unless you worked in the field of superheavy chemical elements, what is the point of all of this?

All of these elements, at least beyond element 98, Californium, have half-lives so short they only exist for a tiny fraction of a second and in quantities that are so small you couldn’t even tell they existed without incredibly sensitive equipment.

While I rattled off the discovery of these elements, other researchers have been searching for different isotopes of many of these elements to see how long their half-lives are. Most are incredibly short, but some are the better part of a minute or even several minutes long.

The first discovery of an element gets the headlines, but what people are searching for is something Glenn Seaborg dubbed “the island of stability.”

The island of stability would be some heavy element, or more accurately, a particular isotope of a heavy element, that would be relatively stable or at least have a very long half-life.

The problem with heavy atoms is that inside the nucleus, there are two opposing forces at work. The electroweak force wants to push protons apart because they have the same electrical charge. However, the strong nuclear force binds them together.

Over very short distances, and I do mean very short, the strong force is more powerful than the electroweak force. However, as an atomic nucleus gets bigger, the distance between some of the protons increases, decreasing the strength of the strong nuclear force. This is believed to be why large atoms tend to be so unstable.

It is believed, or hoped, that a configuration of neutrons exists that would provide stability to a large atom. Based on the mathematics of how isotopes of other atoms behave, it is thought that one of the best hopes for a stable large atom would be an isotope at elements 114, 120, or 126.

However, those haven’t been discovered yet, but researchers in Dubna, Russia, are working on creating 119 and 120 as I record this.

If an island of stability could be found, it could usher in a new understanding of the atom as well as maybe a new era in materials science.

Finding the island of stability, if it even exists, will take a lot of work and a lot of time.

So the next time you take a look at the periodic table, look down near the bottom and give a moment to the elements that were created in a laboratory, only to exist for a fraction of a second.

The Executive Producer of Everything Everywhere Daily is Charles Daniel.

The associate producers are Peter Bennett and Cameron Kieffer.

Today’s review comes from listener manayunk wall over on Apple Podcasts in the United States. They write:

would you like some podcasts with your advertisements?? Ridiculous! There are more advertisement minutes than podcast content in this!! Absolutely ridiculous!! One star!

Ok, manayunk wall, I hate to point out the obvious, but there are not more minutes of advertising than there is podcast content. In fact, it isn’t even close, and everyone listening to this knows that.

This podcast has two one-minute ads. That’s it. They are scheduled in such a way that they are not awkwardly dropped into the middle of the show’s main content, and that is by design. It has been that way since episode one.

The total length of an episode can vary a bit, but the average amount of time taken up by ads in an average episode is about 15% for a 13-minute podcast.

15% is less than the amount of time taken up by ads in most major podcasts. It is less than the amount of advertising on an average hour of terrestrial radio, and it is less than the amount of time for ads on broadcast television in the United States.

So, you are factually wrong several times over, and given the ad load of this podcast compared to other podcasts and other forms of media, I can sleep well at night.

Remember that if you leave a review or send me a boostagram, even a one-star review, you too can have it read on the show.