Let’s imagine we are playing one of those games where you have to draw or describe something and everyone else has to guess. The object you’re given is a science classroom. What would you describe or draw? Test tubes? Beakers?  Bubbling liquids and vivid colours?

What about a table? Not a wooden piece of furniture with legs and gum underneath, but a table with rows and columns; a table that contains everything in our world, other worlds and even our lives. This table can be seen in every science classroom, laboratory and chemistry textbook and has been around for decades. You will have seen it, your parents will have seen it and even your grandparents might have seen it, although it may have looked smaller! This is of course the periodic table of elements, the scrabble tiles of chemistry that list every element known to us.

The modern periodic table containing all 118 elements

This year marks the 150th anniversary since Dmitri Mendeleev published his version of the periodic table, upon which our current one is based. Whilst he was not the first person to try and arrange the elements, his grouping became widely accepted. Mendeleev also left gaps in his table where he believed new elements would sit should they be discovered. One of the greatest successes of Mendeleev’s table was the prediction he made of previously unknown elements and their place in the table.

So, we have this incredible table that brings together all the elements and arranges them in a very specific way so that it works whether you read it from up to down or left to right.  But how then are we meant to read it? In simple terms, the periodic table is formed from a combination of periods and groups. Periods refer to the rows of the periodic table and correspond to an increase in atomic number, the number of protons (positively charged particles) found at the centre (nucleus) of an atom. Groups, the columns of the periodic table, contain elements that all have similar chemical properties. The periodic table can also be viewed as having metals on the left and centre (with the exception of hydrogen) and non-metals on the right. Finally, we can split the table into blocks that give us information about the electrons (negatively charged particles that surround the nucleus) and how they are arranged.

Whole book chapters, and indeed books, have been written on the periodic table, detailing its history, layout, alternate structure and even controversies.  At this point, we will leave these all behind and look directly at its contents: the elements. There are currently 118 different elements, although most people will only have heard of a small number of the more well-known ones. Regular viewers of BBC1’s Pointless over the last decade will perhaps recognise some of the more obscure elements. Even so, they are unlikely to know how they are used, their history and unique chemistry.

Despite this author’s personal enthusiasm, you will be pleased and relieved to hear that all 118 elements will not be described in this article. There are, however, several books that already do this, along with numerous websites. Here, the focus will be on the more unusual, unknown elements, those not usually mentioned, hiding secrets or appearing where you might not expect. Given the large number of elements, this article will be split into two parts. In this first part we will explore the lighter elements, but don’t be fooled they are not all jolly and friendly. We will explore the dull, boring elements, the widely explosive and those that are equally essential and deadly for life. As you read this, should you wish to refer to the periodic table, we recommend looking at this website: https://www.ptable.com/.

Elements 1 – 10: Hydrogen to Neon

The first ten elements, from hydrogen (H) through to neon (Ne), are well known by most people, the exceptions being beryllium and boron. Beryllium (Be), element number four, appears as a silvery, white metal. It is found mainly in minerals such as beryl, which has the chemical formula Be3Al2Si6O18, and includes the gem stones emerald and aquamarine.  Beryllium is said to taste like sugar, but before you start baking a cake with it, be aware it can become toxic quite quickly. Breathing in beryllium dust can damage your lungs, causing them to become inflamed and scarred.  Despite this, it is used in metal alloys to make springs and high-speed aircrafts. Its unusual ability to absorb tiny, tiny particles called neutrons makes it ideal for use in the nuclear industry.

You are most likely to find and use boron (B) as a compound called borosilicate. This compound is a type of glass which includes the well-known Pyrex brand. The addition of boron to the glass makes it tough and heat-resistant, perfect for use in ovens, microwaves and holding very hot liquids.  Another important boron compound is sodium tetraborate, more commonly known as Borax. Borax has been used in cleaning products and flame retardants (to slow down fires).  A fun science experiment is creating goop / slime by mixing borax and glue. The more borax you add, the more rubbery the slime becomes. 

Beryllium containing emeralds may be sparkling and beautiful, but who doesn’t love some boron containing slime!?

Elements 11 – 18: Sodium to Argon

The elements from number 11 to 18 are common and familiar either for their importance in our bodies or in the materials and electronics they help to build. Argon (Ar), however, is probably the one element in this row you haven’t heard much about. But, before you get too excited, there is a reason you never hear much about Argon… it’s such a boring, dull element. In fact, the name Argon means lazy or inactive. Argon’s place in the periodic table is in group 8, a group known as the noble gases. The elements in group 8 are unreactive and really do not do much at all, we call them inert. This dull personality means that they very rarely react with anything. Their inertness does have some uses though and argon is often used in electric lighting, to provide an inert atmosphere inside the bulb.  Argon is also used to create lasers for treating a range of eye conditions.   

Argon was the most noble of noble gases, but very dull and never reacted to anything.

Elements 19 – 36: Potassium to Krypton

As we move further down the periodic table, we begin to move towards a wider range of metallic elements and encounter more of the less well-known ones. Scandium (Sc) is the first element in a block known as the transition metals. When scandium was discovered it was found to fit in one of the gaps Mendeleev left in his periodic table. There are few major uses for scandium, although anyone who plays lacrosse might own a stick containing the element.

When combined with oxygen, scandium oxide (Sc2O3) is used in high-intensity discharge lamps, such as the lights you will find in outdoor floodlights. The addition of scandium tri-iodide (SiI3, a compound of scandium and iodine) causes the light to look more natural. One curious use of this element is in agriculture, where Sc2(SO4)3 is used to help seeds germinate, this is the science term for when seeds begin to grow.  

Most of the first row transition elements are familiar to us: titanium (Ti), iron (Fe), nickel (Ni) and copper (Cu). Vanadium (V), element 23, is an interesting element. Its main use is in alloys, especially steel, to help make it stronger and lighter. Its biological role, however, is a bit more mysterious. Vanadium is believed to be an important element in the body. The problem is, no one knows exactly what it does. Even worse is that some vanadium compounds are actually toxic to us. It is estimated that humans might only need 2 micrograms (a millionth of a gram) per day. You are most likely to get your daily vanadium from wheat and potatoes, with the highest amounts coming from seafood and liver. Some sea creatures are known to have green blood because it contains vanadium. In fact, one of the symptoms of taking in too much vanadium is a green tongue!   

Element number 31, gallium (Ga) is a soft, silvery / blue metal with some very cool and important properties. Unlike most other metals, gallium melts at the low temperature of 29.8 °C. Since our skin is warmer, this means that if you were to hold a lump of gallium in your hand it would quite quickly melt. This has led to a practical joke of giving someone a gallium spoon to stir their cup of tea. As you might have already guessed, the spoon melts when stirring the tea, leaving the tea maker very confused and shocked![1] Luckily, a small amount of gallium in its pure, metal form is not toxic. 

The problem with chemistry
Is when making a cup of tea
A gallium spoon
Melts away soon
Upsetting our friend Dmitri

The most important use of gallium is in the compounds gallium arsenide (GaAs) and gallium nitride (GaN) both of which are important semi-conductors used in the electronics of mobile phones. They are also used in light-emitting diodes and solar cells like those used in satellites and Mars Exploration Rovers.

Right next to gallium you will find the next element of interest, germanium (Ge). Like its neighbour, germanium is mostly found in semi-conductors and solar cells, possibly even replacing GaAs for use in smart phones and computers. Germanium oxide (GeO2) is used in the production of wide-angle lenses and fibre-optic cables. Many of you will have heard of silicon as being vital for all our electrical products; however the very first transistors were actually made using germanium instead.

In our periodic table playground, selenium (Se) is most definitely the see-saw. This element is vital for humans, but having too much of it is actually toxic. However, avoiding it all together is bad, as too little selenium is also harmful. Thankfully, we only need about 60 – 75 micrograms per day, which is easily obtained through cereals and bread. Foods high in selenium include Brazil nuts and black treacle – unfortunately selenium deficiency is no excuse to start eating treacle out the tin!  As well as eating it, you might be putting selenium in your hair. Selenium disulphide (SeS2) is commonly used in anti-dandruff shampoo as it prevents fungal growth from irritating your scalp. A curious property of selenium is that is conducts electricity better when light shines on it. This made it ideal for use in photocopiers, although the use of selenium has declined over the years.

See-saw selenium; it’s important to get the right balance.

Elements 37 – 56: Rubidium to Barium

As we continue further down the periodic table, most people will only recognise those elements that have been known since ancient times: silver, tin, gold, mercury and lead. These elements are also unusual as being part of a small group that have chemical symbols completely different from their names. Because these elements have been known for so long, their symbols tend to come from their ancient name. Details are given in the table below.

Modern Name and Symbol Ancient /
Alternate Name
Named After
Sodium (Na)natron (derived from ancient EgyptianMineral of sodium carbonate
kali (from word alkali derived from Arabic)Arabic word for plant ashes
Copper (Cu)aes cyprium (Latin – later cuprum)Cyprus, the main source of copper in Roman era
Silver (Ag)argentum (Latin)Latin for silver, meaning white or shiny
Tin (Sn)stannum (Latin)Eventual Latin word for tin
stibium (Latin – taken from Greek, retaken from Arabic / Egyptian)Latin / Greek name for antimony. Possibly from Arabic / Egyptian describing eye makeup
( W )
Wolfram (German)Mineral wolframite, itself named from german (wolf rahm) meaning wolf’s scream
Gold (Au)aurum (Latin)Latin word for gold
Mercury (Hg)hydrargyrum (Latin form of Greek)Word meaning “water-silver” describing mercury’s look
Lead (Pb)plumbum (Latin)Latin word for lead

Element number 39 is yttrium ((Y) said like it-tree-um), a silver-white metal. It is used mainly in alloys, where small amounts are added to improve the property of the material.  A form[2] (known as an isotope) of yttrium called Y90 is used in the treatment of cancer. When combined with aluminium and oxygen, yttrium is used to create a material called YAG, which can be used to produce lasers. Yttrium is named after the village in Sweden where it was discovered, Ytterby. This place has a special connection to the periodic table as another three elements: ytterbium, erbium and terbium are all named after it.

Technetium (Tc), element number 43, is part of the second row of transition metals. This elusive element remained hidden for a very long time because of its unusual chemistry. It is the lightest element for which there are no stable forms (isotopes). In other words, every form of technetium is radioactive, which means over time it will decay away and change into one of its neighbours, molybdenum (Mo) or rubidium (Ru). The isotope with the slowest decay rate only lasted for around four millions years. This may sound a very long time, but when you consider the Earth is 4.5 billion years old, it is not surprising that nearly all the technetium on Earth has gone. Because of its rarity and habit of decaying, there are limited uses for technetium. The major use is in medicine where it can be used as a radioactive tracer to find and determine any problems in our bodies.

Antimony (Sb) was historically also used as a medicine. One use was as a laxative (a substance that makes you go to the toilet) and involved swallowing a small, round ball of antimony. This would work itself through your body and make you go to the loo. The antimony ball would come out unchanged and so could be extracted, cleaned (hopefully!) and kept ready for its next use. Antimony has not been used as a medicine for a long time now, which is lucky given it is actually toxic.

Antimony is often made into an alloy with lead and used for batteries, bullets and ball bearings. The oxide of antimony (Sb2O3) is used as a flame retardant. One of the strongest acids ever produced contains antimony. Fluoro-antimonic acid is a combination of antimony pentafluoride (SbF5) and hydrogen fluoride (HF). This superacid is 10 billion billion times stronger than sulphuric acid and reacts violently with water. It cannot be stored in glass containers as the acid will dissolve it and instead must be kept in Teflon lined containers.

‘Elementary, my dear Watson, when I reached into this container I discovered there to be no technetium inside. Oh, I say – I do believe my hand has dissolved to the bone… ‘

Next to antimony lies tellurium (Te), element number 52, a brittle, silvery-white metalloid. Its place on the periodic table initially caused much confusion for Mendeleev, as its atomic weight is higher than the next element, iodine, yet comes before it. Eventually, following the discovery of isotopes, it was determined that the majority of tellurium existed as the heavier isotopes, causing the average mass of the element is be higher than iodine. Tellurium and its compounds are slightly toxic, but poisoning can occur with some very horrible symptoms. Even small amounts of it can result in “garlic breath” and a smelly body odour, caused by the production of dimethyl telluride (CH3)2Te. Despite this, tellurium oxide has found use in re-writable CDs and DVDs.

Xenon (Xe) is another boring, inert noble gas, but does have one quirk. We are all familiar with how helium can be used to give people a funny, squeaky high-pitched voice. Well, xenon has the opposite affect and when inhaled gives you a much, much deeper voice. However, the inhalation of xenon, like many other gases, can be dangerous, especially as it can prevent the intake of oxygen and lead to asphyxiation, which can result in unconsciousness and death!

The final element in this episode of our periodic drama is number 55, caesium and is the perfect element for an explosive ending. Caesium (Cs) is a soft, silvery-gold metal that is very nearly a liquid at room temperature. Its melting point is a rather mild 28.5°C, lower than our disappearing spoon element, gallium. However, you wouldn’t want to make a spoon out of caesium. For one thing, it is a relatively rare element to find, but perhaps more dangerous is its reactivity. Left out in the open, caesium ignites spontaneously in air and reacts violently with water – not ideal for stirring your cup of tea! Caesium has few uses, but one of its most important, and perhaps unknown, is as a clock.

Many old or grand clocks, such as the iconic Grandfather Clock, often contain a pendulum that swings hypnotically back and forth, back and forth, back and forth. The swinging motion of the pendulum is set so that the frequency of one swing equals one second. In atomic clocks, the frequency is based on the movement on an electron between two different, but very exact, states of different energy in caesium atoms. However, unlike our swinging pendulum, one second is defined by the number of cycles the electrons move between these states. It just so happens that one second is equivalent to over 9 billion cycles (the exact number is 9 192 631 770 cycles). This incredibly high level of accuracy means that atomic clocks have an error of one second every 100 million years. International time, electronic communication and GPS are all set using caesium atomic clocks.

Earlier we met fluoro-antimonic acid, one of the strongest acids ever made. By contrast, caesium hydroxide (CsOH) is a very strong base (the opposite of an acid) and is often classed as the strongest alkali [3] . Like its acid counterpart, caesium hydroxide is so strong that it will actually react with glass and has to be stored in special plastic containers. Another sinister feature of caesium is the isotope caesium-137. This is a radioactive form of the element and is a common product from nuclear reactors and weapons. The radiation emitted from caesium-137 is very dangerous and was one of the main radioactive substances present in the surrounding area following the Chernobyl nuclear disaster.

This ends part I of our tour across the unknown, unusual and unnerving elements of the periodic table. In part II we meet some of the densest and most precious metals, some of the most toxic and some of the rarest naturally occurring. We will enter a whole new world of man-made elements: atoms that exist for fractions of a second and elements whose entire existence has only ever consisted of a handful of atoms. Be prepared for nuclear explosions, spy assassinations and smashing atoms together at super fast speeds!

[1] Search for Gallium Spoon on YouTube for a video demonstration. BACK TO POST

[2] Technically this is known as an isotope. An isotope of an element has the same number of protons in its nucleus but a different number of neutrons, changing its weight. This can also make its nucleus unstable causing it to be radioactive. BACK TO POST

[3] An alkali is essentially a base that is soluble in water, it can be thought of as a subset of bases. CsOH is the strongest alkali in the sense that anything stronger actually reacts with water, rather than dissolving in it. BACK TO POST

This article was written by Marcus Taylor.


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