The periodic table is a way of listing and categorising all the known elements: every known element is ordered 1 – 116 according to their ‘atomic number’, with the lightest elements being at the top of the table.
The simplest answer to the question of which is the most useless element in the periodic table are the unstable transuranium elements (these are after uranium in the table). All elements after lead (atomic number 82) are radioactive and unstable: their atoms ‘split’ apart, turning into different elements and releasing energy. Uranium (92) is the last radioactive element that can be around for a substantial length of time, elements with atoms larger than uranium generally have half-lives (a measure of how long they stay intact for) less than the age of Earth – meaning any naturally occurring atoms will have mostly decayed into another element. Hence, the most useless elements would be those that are so radioactive that they do not occur in nature and break up almost the instant scientists make them! So when considering the transuranium elements from mendelevium (101) to livermorium (116) (the most recently discovered and confirmed element) only a few atoms of each element have ever been made at any one time!
This answer is something of a cop-out however (who ever heard of livermorium?) so it’s probably a little more informative to consider not the whole periodic table, but rather just the elements 1 though 92, which are naturally found on Earth:
Thulium (69) often receives quite a bad reputation for being useless. Not only is thulium extremely expensive and rare but the first person to isolate a pure sample in 1911 had to process his sample a staggering 15,000 times! Despite this, it has since found use in portable x-ray machines, so it’s not a totally useless element. Given this, I would suggest francium (87) to possibly be the most useless element. First discovered in France (hence the name), it can be found naturally in the earth’s crust in the mineral uraninite – but it’s believed that as little as 20-30g is present in the world at any one time due to francium being incredibly short-lived. Furthermore, no large quantity of francium has ever been made: within two hours nearly all (97%) of a sample would have disappeared! And because it is so radioactive, the heat given off from any large sample would cause it to vaporise almost instantly! This is probably the reason that it took until 1939 to discover francium and why it was the last element to be isolated from nature and not created synthetically in the lab.
Read more: For an excellent version of the periodic table and its elements you can visit the RSC (the Royal Society of Chemistry, not the Royal Shakespeare Company!) website here: http://www.rsc.org/periodic-table. Or another good website is the periodic table of videos, where you can spend an entire afternoon learning about the elements: http://www.periodicvideos.com/
Answer by Kane Heard
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