The Element of Surprise: Things You Didn’t Know About The Periodic Table

Dan Chesman

If you were to walk into any school science laboratory and not see a periodic table on the wall, I would eat my own underwear. This seemingly unordered array of squares in a sort-of-but-not-really-rectangular shape takes its mammoth foot and stamps on your tiny ant of an Excel spreadsheet. It’s probably the most concise bit of database compiling you’ll ever see. Some would say that it’s art.

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Almost as good as the periodic table.

Image Credit: Wikimedia Commons

Though many laid the foundations, it is Dmitri Mendeleev’s first incarnation of the periodic table that gets all the credit. According to the Royal Society of Chemistry, his arrangement of the properties of elements correlated almost perfectly with the atomic weight of the known elements at the time. He noticed there were gaps, and went on to predict the properties of the elements that filled these gaps. By 1886, scandium, gallium and germanium had all been discovered based on Mendeleev’s predictions, and his method forms the basis of the modern periodic table. What a hero.

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This story’s bearded hero, Dmitri Mendeleev

Image Credit: The Telegraph

But what about these elements? Chemistry is weird and wonderful (and also really irritating – ask any PhD student how their lab work went this week!) and the elements form the basis of all the funky little molecules that do all the cool stuff we love.

By far, the best and most versatile group of elements are the transition metals. These are the three rows sat in the centre of the periodic table, with scandium at the top right and mercury at bottom left, among a few additional ones in a fourth row. These elements are responsible for much of the colour we see in the laboratory, and their compounds do a whole host of important things: from catalysing the manufacture of cling-film (titanium compounds) to curing cancer (cisplatin, a platinum compound with two NH3 and two chlorine (Cl) groups arranged around a central platinum atom).

Did you know that sodium (Na) in your table salt (sodium chloride) will catch fire if you put a chunk of the pure metal in water? Move one element down, and potassium will explode. Move to the second bottom row, and a few grams of caesium might demolish your house. These elements, the alkali metals – named because their reaction with water forms an alkaline solution – ignite on reaction with water because they have one very loosely bound electron which they will do anything to get rid of. As you move down the group, the elements hold on to their electron more loosely and will throw it at whatever will take it with ever more ferocity.

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Colours in transition metal compounds

Image Credit: chemguide.co.uk

In stark contrast, one left of the top right of the periodic table, is fluorine. This is one short of a full shell of 8 electrons and if caesium were to throw its electron toward it, fluorine would probably rugby tackle it to the ground. Fluorine is massively reactive for precisely the opposite reason to caesium. It will do anything to steal an electron.  Get even a whiff of this stuff, and you’ll be on the floor in a heap.

What about the other elements? Did you know that humanity has created its own elements? The first was technetium, which can be found in any hospital, where it is used as an imaging agent. Others include flerovium and livermorium, as well as the new kids on the block: nihonium, moscovium, tennessine and oganesson. These last four were named as recently as June 2016!

Some of the more exotic and rare elements lie on the bottom two rows of the periodic table. These are known as the lanthanides and actinides, or the f-block elements. These do all kinds of cool things. Many of them are man-made, and some named in honour of famous scientists (einsteinium, fermium, nobelium…). The top row – the lanthanides – are used in many fields from medical imaging to lighting your TV. Gadolinium is used to enhance the contrast of MRI scans, making it possible to diagnose diseases such as cancer and brain tumours. Europium is found in old TVs to give a red colour, and americium (an actinide, the bottom row) is a key component in your smoke alarm.

What’s the best element though? They’re all in with a shout really, but purely for being the real element of surprise, the award goes to mercury.  It’s one of the most toxic things you can come across, and it has baffled scientists for years. It’s a liquid, one of only two in the periodic table, and a heavy metal. Based on its position, it should not be a liquid, and it’s only recently that scientists have come up with a plausible hypothesis as to why this is the case – relativity. Yet again, Einstein has the answer.

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