Teach your students the Alphabet of the Universe!
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Take a look around you. Have a look at the objects in your room, outside at the trees, birds and sky, and then think about everything else in the world. I’m sure you’ll find the variety and complexity of the world’s different materials amazing. But what is truly astounding, is that everything you see is merely the result of a combination of elements, of which (naturally occurring) there are only 92 to choose from.
But what is more incredible, is that it is highly likely (virtually certain) that the whole Universe is the same; a combination of the selection of these 92 elements. Fascinating!
What is an element?
An element is a substance that is made up of only one type of atom. Oxygen gas is made up of only Oxygen atoms, as a strip of Magnesium metal is made up of only Magnesium atoms. Basically, it is something that cannot be broken down into anything simpler.
If you look around you, you will struggle to find examples of elements. The ‘lead’ in your pencil is made of only carbon, as is diamond, as is the black charred substance on your burnt toast! As you may have gathered, carbon is a little complex and immensely important.
You may also have silver, gold or platinum as jewellery. It is possible that you have aluminium foil in your drawer, and you may have seen the copper in your electrical wires or water pipes, and your car may be rusting due to it being iron, but apart from that, elements are hard to find. This is because they mainly exist as compounds.
A Compounding Problem
The English language has 26 letters in its alphabet. Some of these letters can exist as words, such as ‘a’ and ‘I’, but most are placed in combinations that allow us to make millions upon millions of different words. Some letters are also more common, such as ‘e’ which is the most commonly used letter in the English language. It is the exact same thing with elements.
Elements bond with different elements to make compounds. When this happens, the properties of the compound are usually vastly different to the elements that make them up. A classic example is when the element sodium, a highly reactive metal that can set on fire in water, reacts with the green, poisonous gas chlorine, to produce the compound sodium chloride. As you may know, this is the chemical name for table salt; a relatively harmless substance that makes your chips taste great! Clearly table salt is different from the two elements that make it, and it is this varying combination of different elements that accounts for the incredibly diverse materials that make up our universe. A massive dictionary from just 92 letters.
The Periodic Table
All elements are arranged on the Periodic Table. They are arranged in such a specific order that you can tell a great deal about an element, simply by its position on the table.
Elements are arranged in order of increasing atomic number from the lightest element Hydrogen, to the heaviest natural element Uranium. I say natural, as there are now over 115 elements, but everything after Uranium has been artificially made in laboratories by humans.
Elements are also arranged in groups, with the first column being group one, the alkali metals and group two being the second column, the alkali Earth metals. Then there is the middle section known as the transition metals, before we get to group three which is the column starting with Boron and containing Aluminium. The next column is group 4, then 5, 6, 7 (the Halogens), finishing with Helium’s column, group 8; the noble gases.
What these groups tell us is how many electrons (sub-atomic particles) are contained in the outer shells of the elements. Electrons orbit the nucleus of an atom which is made up of the sub-atomic particles called protons and neutrons. They orbit in clouds but also in shells. How many electrons are in the outer shell determines the element’s behaviour, how it reacts and how it bonds with other elements.
As Lithium, Sodium and Potassium are all in group one, they all have one electron in their outer shell. This means that they are extremely reactive as their outer shell is not full so they do what they can to bond to non-metal elements (at the top right hand side of the table). They need to get rid of their one electron.
Chlorine on the other hand is in group 7 and is desperate to gain an electron to make it stable which will complete its outer shell. It therefore happily reacts and bonds with sodium, resulting in sodium chloride where the sodium has ‘given’ its electron to chlorine.
The group 8 elements already have full outer shells, which means they are already in a stable state, therefore they don’t have to lose or gain electrons, resulting in them being inert. They are unreactive and stable and because of this, exist as elements and not compounds.
The rows of the periodic table are known as periods and dictate how many shells the elements have. So if you look at Magnesium, you can tell it has two electrons in its outer shell as it is in group 2, and it has three electron shells as it is in period 3. Clever!
The elements in their respective groups also react in similar ways. You can see trends in their behaviour which is another reason for their grouping. The periodic table really is a work of genius and a work of art!
Mendeleev was a Russian scientist whose work on the periodic table defined its modern form. You will be pushed to find a chemistry classroom anywhere in the world that does not have a periodic table on the wall. His work on the periodic table and the properties of elements has shaped our understanding of not only the world, but of the universe. His importance as a scientist cannot be overstated.
When he was alive (1834-1907) there were only 63 known elements. He managed to arrange these elements into groups depending on their atomic weight and their similar properties. He then left gaps in the table as to where unknown and undiscovered elements were to go, and he accurately described their appearance, reactivity and properties based on the properties of elements around them. When these elements were discovered, his predictions and descriptions were incredibly accurate. This is truly staggering!
What’s in a Name?
All of the elements on the periodic table have chemical symbols which are recognized internationally. Some symbols, such as Na for Sodium, appear not to make sense, but many of them are symbols from their Latin or Greek names. Fe comes from the Latin Ferrum which we know as Iron. Au, also Latin, means Aurum which we know as Gold, but my favourite is Pb which stands for Plumbum! We know this as Lead, which is why plumbers are known as such, as when the profession originated, water pipes were made from lead. Clever!
The Usual Suspects
Hydrogen is by far the most common element in the universe as it makes up the majority of a star’s mass. On Earth, Oxygen, Iron, Aluminium, Silicon, Sodium, Potassium, Carbon and Magnesium are among the most common within the Earth’s crust and their importance relates directly to us. Our planet dictates which elements we use and our bodies contain all of these elements in various forms.
The most important element to life though, is unquestionably Carbon. Carbon is essential to all known life and could not exist without it. You are a combination of mainly Carbon, Oxygen, Hydrogen, Iron, Calcium, Phosphorus and Nitrogen but there’s even a trace of Arsenic in you, amongst other elements. It is the combination of so few elements that create an incredibly diverse universe. “Elementary my dear Watson”!