Last week, we were talking about elements and isotopes.
In particular, I made the comment that you could make gold from lead. It is possible but very, very expensive. It would cost way more money to make gold than the gold itself would be worth.
However, the idea that atoms are not permanent was shocking to scientists studying atoms in the late 1800s and proved fundamental to the development of a theory of the atom in the first decades of the 1900s.
Throughout our history, human cultures have believed in the permanence of matter. The sun and stars were permanent fixtures in the sky. The plants, animals, and rocks around us were fixtures on Earth.
Yes, a rock could be heated and new material obtained. For example, heating malachite results in copper. But the belief was that the additional heat just added more of one of the four essential elements. More fire simply transmuted rock to metal.
However, as our modern understanding of the world evolved, scientists came to understand that everything around us is built from some 92 naturally occurring elements.
I say "some" because although all of the elements up to uranium are considered "naturally occurring", at least one of those elements isn't found in nature. Technetium - element 43 - does not have a naturally occurring isotope.
And a few others - francium, astatine, radium - could be considered transitory at best.
As scientists filled in the periodic table, each element was carefully analyzed and placed in its appropriate position and while the rocks or stars might not be permanent, the belief in the late 1800s was that atoms were.
Starting with the observations of Henri Becquerel and J.J. Thomson, and following with the research of Pierre and Marie Curie, the notion that atoms could be broken down into smaller pieces revolutionized our understanding of the universe.
The Curies' work was critical in isolating and identifying many of the radioactive elements which are daughters of Uranium-238. The work of many subsequent scientists resulted in the identification of three major decay chains - The Thorium Series, The Actinium Series, and The Radium or Uranium Series.
Respectively, these chains result from the decay of Thorium-232, Uranium-235, and Uranium-238. All three chains eventually produce various isotopes of lead. The isotopic composition of lead differs greatly, depending upon the source, and has been used to date the age of the Earth.
Lead represents the "first stable heavy isotope" in the decay sequence. It is the end point for the naturally occurring disintegration of nuclei and making smaller atoms, such as gold, is difficult.
However, the natural radioactive decay sequences are not the only tool in the scientist's kit. It is also possible for an atom to undergo a fission reaction. Understanding how to break up the atomic nucleus is the research that ultimately led to the development of nuclear energy and the atomic bomb.
Uranium atoms, for example, can be broken into two daughter nuclei and a smattering of neutrons. With the careful moderation of the neutrons, a self-sustaining chain reaction can be maintained. The heat released can be used to make steam and eventually electricity.
In the 1940s, scientists also realized that hydrogen nuclei could be fused together to build larger atoms. This is the reaction that occurs at the core of the sun. Four hydrogen fuse to form a helium; three helium make a carbon; and so on, until eventually a star is made of nothing but iron.
In the 1950s, physicists came to realize that they could use a similar principle to build super-heavy atoms. They could fuse together smaller nuclei to build big ones.
In essence, they would be reversing the fission reaction in a nuclear power plant or super-sizing the fusion reactions of the Sun.
By colliding the nuclei of helium with uranium, heavier elements could be formed. Repeating the process resulted in a number of new elements such as Americium and Berkelium. Much of this work was carried out by Glenn Seaborg and he is credited with being the principal or co-discoverer of 10 trans-uranic elements.
But to really push the limits of atom building, we need to go beyond colliding atoms with helium nuclei. We need to smash together much bigger pieces.
In 2010, element 117 or eka-astatine was created using a berkelium target and a beam of calcium ions moving at a significant fraction of the speed of light. The collision only produced a few atoms of the super-heavy element but the results suggested that the experiment had worked.
This past month, physicists confirmed the results. Element-117 can now be included in the periodic table of elements. Only 4 or 5 atoms have been made but that is sufficient to answer almost all of the outstanding questions.
Indeed, the only question that remains is what should it be called?
