Happy Centenary Glenn Seaborg!

Happy Centenary Glenn Seaborg!


Feted during his lifetime, reviled by some, forgotten by many – why should we remember Glenn Seaborg in this centenary year of his birth? His work has little relevance to GCSE or even A level Chemistry but in fact he was one of the most influential chemists of the twentieth century and perhaps we can spare a moment from examination preparation to consider the part he played.

Glenn Seaborg was born in April 1912 in a mining town in eastern USA. His parents were Swedish. In 1922 the family moved to California but his father struggled to make a living. Glenn did part-time jobs to pay his way through a chemistry degree and in 1937 completed a doctorate at the University of California at Berkeley. He stayed on as an assistant and instructor working on acids and bases with Gilbert Lewis.

Exciting new work was going on at Berkeley using the cyclotron built by Ernest Lawrence. Lawrence and his team of physicists used the cyclotron to fire charged particles at targets made of various elements. In 1940 the team produced the first artificial element, number 93, named neptunium as it followed uranium. Seaborg was asked to use his chemical skills to separate and identify the products of the bombardments which he did in his spare time. In 1941 Seaborg was fully involved in the isolation of the next element, number 94, plutonium. Over the following 33 years Seaborg led the team that produced a further eight of the “trans-uranic” elements the last being number 106 in 1974. No other person has been involved with the discovery of more elements.

In 1951 Seaborg was awarded the Nobel Prize for his work and in 1997 received a unique accolade. His last new element was officially named Seaborgium. This is the only time an element has been named after a living person. Seaborg died in 1999.

Another reason for remembering Glenn Seaborg is that he is responsible for the version of the Periodic Table that has hung on chemistry laboratory walls for the last sixty or so years. In school courses we celebrate Mendeleev’s Periodic Table but in fact it does not look much like the modern version. This is because Bohr’s model of electron shells changed our understanding of how the elements are built up. In the 1930s elements were arranged as today with 8 main groups and the transition metals in a central block with the fifteen lanthanide elements (from lanthanum, 57, to lutetium, 71) in a separate row, usually tacked at the bottom of the table. Most chemists placed the four elements from actinium (89) to uranium (92) in the transition metal block. Seaborg studied the properties of the trans-uranic elements, particularly americium and curium, isolated in 1944, and became convinced that the fifteen elements from actinium should in fact be in a row under the lanthanides. This is where they are found today.

During the Second World War Seaborg’s work was top secret because it was discovered that an isotope of plutonium was spontaneously fissile. This means that the atoms split roughly in half releasing neutrons and a huge amount of energy. Seaborg was brought into the atomic bomb project. There were in fact two groups working on “the bomb”. One group designed a bomb using naturally occurring uranium which was detonated over Hiroshima in August 1945. Seaborg’s team extracted atoms of plutonium-239 made by nuclear reactions. The work was slow and very dangerous as plutonium is highly toxic and radioactive. This material was used in the second bomb that was dropped on Nagasaki.

Seaborg knew how powerful the bomb would be and that there would be a huge number of deaths if it was used. He supported the idea of demonstrating the bomb to the Japanese by setting it off on an uninhabited island. The US military officials didn’t accept this idea, probably because there was not enough plutonium to make another bomb quickly. In the 1960s Seaborg served on the US Atomic Energy Commission helping in the negotiation of the UN Non-proliferation Treaty that held back the development of nuclear weapons.

Despite advising presidents, Seaborg spent his whole working life at Berkeley and was married from 1942 until his death to Helen, Ernest Lawrence’s secretary. They had six children.

Activities

1 Glenn Seaborg’s team discovered elements numbered 94, 95, 96, 97, 98, 99, 100, 101, 102 and 106.

(a) Find out the names that these elements have been given

(b) What or who have the elements been named after?

(c) What is the most recent element (i) to be given a name, and (ii) to be discovered (probably).
2 The first eleven trans-uranic elements fit in the actinide series at the bottom of the Periodic Table, but where is Seaborgium (106)? Name an element that Seaborgium resembles.
3 Discuss the part that Seaborg played in the atomic bomb project. Was his role important? Do you think he intended to cause the deaths of many thousands of people? Was the work on the second bomb justified?

4 How should we celebrate Glenn Seaborg’s centenary?

Bibliography: Mike Sutton, To plutonium and beyond, Chemistry World, vol 09, no. 03 pub Royal Society of Chemistry, March 2012.