And if we draw it, it would look a little bit like this. We've got one carbon atom and two oxygen atoms.
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Katie: So, carbon dioxide means a carbon plus two oxygens. Katie: And 'di' means two, so dioxide means two oxygens?ĭr. Katie: Yes, so that's carbon and dioxide. Now, another one you'll have heard of is carbon dioxide. We use the numbers to show how many of each atom there are in a compound. For example, water, there are two hydrogens and just one oxygen. When a compound forms there isn't always an equal number of elements. So we've got our oxygen atom and then we've got our two hydrogen atoms. And if we were to draw the molecule, it would look a little bit like this.
And the two is because for every one oxygen atom there are two hydrogen atoms in water. Now, we always put these numbers down at the bottom when we're writing chemical formula and this number, it shows how many of each type of atom we have in the compound. We've got water with the chemical formula H₂O. Oxygen, which you've already found, and hydrogen. Katie: So which chemicals is water made up of?ĭr. So, since water is a compound, it means its chemical formula is made up from elements that we can pick from the periodic table. And atoms, they chemically bond together in a fixed ratio to make a compound, and this means we can describe these compounds with a chemical formula. Tim: A compound is a pure substance which is made from more than one element. And, remember, we only show pure elements on the periodic table.ĭr. Tim: Water isn't an element, it's a compound. And tungsten is actually what the filament of some light bulbs is made from, the little spiral filament that lights up when you switch it on.ĭr. W is actually the element tungsten, and the W symbol comes from the mineral in which tungsten is found called wolframite. Tim: It would be easier, but you know the history of who discovered these elements and when and where is really long and complicated and interesting and the symbols for some of the elements are left over from their old names.įor example, the symbol for iron, Fe, comes from the Latin name for iron, ferrum. That would be much easier to remember, wouldn't it?ĭr. Katie: OK, so why is it Fe and not Ir like a shortened version of Iron. Some elements have two letters in their symbol, because there are more than 100 elements, but there are only 26 letters in the alphabet, so we have to double some of them up. Fe is actually iron and you can tell this is an element because it's got an uppercase F followed by a lowercase e. Now, remember, on the periodic table we only put elements, not compounds. Katie: I recognise Fe but if it's got two letters like that, does that mean that it's two elements combined?ĭr. Are there any symbols that you recognise? Any elements that you might know?ĭr. And the formula of sulfuric acid is H₂SO4.Īnd this tells us that one molecule of sulfuric acid contains two hydrogen atoms, one sulfur atom and four oxygen atoms.ĭr. Butane, which has the chemical formula C₄H₁₀, has four carbon atoms and ten hydrogen atoms. The chemical formula for Magnesium Oxide, MgO, tells us that there is one atom of magnesium for every one atom of oxygen. They often, but not always, have little numbers called subscripts that show how many atoms of each element are present in one molecule of a compound. VOICEOVER: Chemical symbols and formulas.Įvery element in the periodic table is represented by a unique chemical symbol, like O for Oxygen or Mg for Magnesium.Ĭhemical formulas represent compounds or elements where more than one atom are bonded together. Well, before we move on, here's some more information to help us understand the basics of chemical symbols and formulae. Katie: Amazing! Thank you very much, Dr Tim. The table is used to arrange the elements and we put chemically similar elements together in groups. There are something like 100, and each has a unique symbol made up of a letter and sometimes two letters. And an element is a pure substance made from only one type of atom. Tim: So this is the periodic table and each letter on it represents a different element. What do they all mean? And what is the table actually used for?ĭr. It's a little bit like a giant game of Scrabble.
Now, we've got part of the periodic table here. And here to explain H to the Cs to the Ns and the Os, it's our super scientist extraordinaire, Dr Tim Gregory. And today it's a chemistry classic, the periodic table.
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