Re: What is the most expensive element on the periodic table.

Sounds like a very simple question, Baz -- just look up some prices and send you back the answer! Unfortunately it just does not work out like that. There are major complications.

1. Are you just wanting the element in whatever chemical form is convenient, or are you wanting the element as a simple substance? It is a lot cheaper and easier to buy your sodium in sodium chloride (common salt) than as metallic sodium, for example.

2. Is purity an issue? There are sometimes extreme increases in cost to get a metal in a particularly pure form. This particularly applies to some of the elements that are found in ores where they are associated with a much more common element with similar properties where separation is difficult (e.g. hafnium and thorium with zirconium, mixtures of rare earth ores, platinum-like metals, etc.).

3. There are quite a few elements on the periodic table that are simply not on the market, and several you could not even pay a contract to buy. It is impossible to define how much something costs if it is not on the market, and there is no supplier.

There are somewhere between 110 and 120 "known" elements on the periodic table. Of these, there are 81 stable elements. The others are all radioactive, which means they gradually decay and disappear. Some take billions of years to do so; others can only be found in forms that decay in a few seconds or less.

The 81 stable elements are those with atomic number 1 (H) to 83 (Bi), but excluding 43 (Tc) and 61 (Pm). Of these, the most expensive are probably from the platinum metal family -- rhodium (45 Rh), osmium (76 Os), or iridium (77 Ir) (but it is hard to find a fair basis of comparison). Hafnium (72 Hf), tantalum (73 Ta), or some of the less abundant "rare earth" metals like lutecium (71 Lu) might be just as expensive if you wanted high purity.

There are 2 radioactive elements that are abundantly present in the natural environment, and not particularly expensive -- uranium (92 U), and thorium (90 Th). They only decay over billions of years.

The elements from polonium (84 Po) to protactinium (91 Pa) are produced in the natural decay processes of uranium and thorium ores, and can be separated from these bodies by chemical means. Astatine (85 At), and francium (87 Fr) can not, since they only last for about 1 day or 1 hour respectively. In practice, usually only radium (88 Ra), which has a lifetime of several thousand years, and a number of uses, is produced. Usually, these elements, if they are wanted, are produced in nuclear reactors, as are (43 Tc), (61 Pm). Technetium (43 Tc) is manufactured and sold in quantity, as it has a number of medical uses.

Elements 93-98 all have isotopes which last from thousands to millions of years. 93-96 can all be made in reactors, and have a number of useful applications. Elements 100 and above have only ever been made a few atoms at a time, and last for only seconds or minutes. You would not be allowed nor able to buy any of them.

Try a google search with "periodic table element price", and after sifting out the sites that are just trying to sell you fancy printed periodic tables, you will find others about getting together a collection of chemical elements, and prices of individual elements. I am not putting in a direct link as I do not wish to give the appearance of endorsing any particular commercial product. Do be discriminating if you want to follow up along these lines, and take safety issues very seriously.