![]() ![]() That is easily put right, of course, by re-writing the equation to start with 2 atoms of magnesium.Īnd that is the proper equation - everything is now balanced on both sides of it. If you leave it like that, it seems that you have by magic generated another magnesium atom out of nowhere. You can do this by writing a big "2" in front of the formula.Ī big number in front of a formula multiplies up the whole formula until you get to a break - the end of the equation, a plus sign, or an arrow, for example.īut beware! By writing that 2, you have messed up the balance of the magnesium. What you need is to form twice as much MgO. You can't just re-write the formula of magnesium oxide as MgO 2 - that doesn't exist! You must never try to balance an equation by changing a formula. What you absolutely must not do is change the formula of the magnesium oxide. So how do you get another oxygen on the right-hand side? You can't just lose an oxygen atom - everything must be accounted for. That means that in the equation we have just written, you seem to have started with 2 atoms of oxygen, but only ended up with 1 in the product. (You will later come across another more mathematical way of looking at this, but that is some distance in the future.) It is pointless going on with this page if you can't do basic things like that.Įach symbol you write counts as one atom (or one ion) of that element. ![]() Note: I know I keep on about this, but if you can't work out that magnesium oxide is MgO, or you didn't know that oxygen goes around in pairs, then you must go back and read the pages about writing formulae. ![]() The next thing you have to do is to translate the names of the substances involved into their formulae.ĭon't forget that oxygen (in common with things like hydrogen and chlorine) goes around in pairs. Still using the example of magnesium burning in oxygen. You have to know what you started with and what you ended up with. In the very early stages of a chemistry course, you might be asked to write word equations - usually for reactions slightly more complicated than this one.īut if you are doing chemistry properly, you may never actually write a word equation down, but it has to be in your mind. The arrow here be translated as "goes to" or "produces" or whatever similar term you want to use. The video displayed this as a simple word equation. Have a look at this YouTube video which is a snippet from a Royal Society of Chemistry lecture, and shows magnesium metal burning in oxygen in the air. You need to know what you started with and what you ended up with. You can't just make up an equation - it has to be based on exactly what happened in a chemical reaction. You need to know what is actually happening! You will need to be reasonably competent at writing formulae for ionic compounds and there is no point in continuing with this page until you are. Don't try to rush it - spending time now will save you a lot of problems later on. This is one of the major hurdles in the subject. Learning to write equations can take quite a lot of time when you are starting chemistry. You have to get this right, because chemistry will be a nightmare to you if you find equations a mystery - it is an essential tool in understanding chemistry. This page explains how to work out equations for simple chemical reactions. How to write symbol equations for simple chemical reactions How to write equations for simple reactions ![]()
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