[Music] hi welcome back to three sighs lessons code UK by the end of this video you should be able to explain what's meant by oxidation and reduction in terms of electrons you should then be able to identify oxidation and reduction in 1/2 equations or in simple equations all of this material is for higher students only in the last video we started looking at displacement reactions such as this one we saw that a more we up development will displace a less reactive element from its compound in this case because magnesium is more reactive than iron it displaces the iron from the iron oxide the iron atoms have been reduced as they've lost oxygen the magnesium atoms have been oxidized as they've gained oxygen now in this video we're looking at another definition of oxidation and reduction this one involves electrons oxidation is the loss of electrons and reduction is the gain of electrons here's an example to illustrate the idea we've got a magnesium atom forming the magnesium ion mg 2 plus and 2 electrons in this case we can see that the magnesium atom has been oxidized as it's lost electrons scientists call equations such as this one 1/2 equation and we're going to be seeing these again in later videos here's another example here a sulfur atom has gained two electrons unformed the sulfide ion we can see that in this case the sulfur atom has been reduced as it has gained electrons now there's a fairly easy way to remember this think of the words oil a twig oxidation is loss of electrons and reduction is a gain of electrons here are two examples for you to try pause the video now and work out whether these are oxidation reactions or reduction reactions okay so this half equation shows an aluminium atoms losing three electrons to form an aluminium ion it the aluminium atom has lost electrons this is an oxidation reaction this half equation shows an oxygen atom gaining two electrons to form an oxide ion this is a reduction reaction as the oxygen atom has gained electrons okay now you could be asked to identify oxidation or reduction reactions in symbol equations here's a typical question identify in the reaction below which element has been oxidized and which has been reduced this shows zinc reacting with copper sulfate to form zinc sulfate and copper this is a displacement reaction now in order to answer this question you need to know the ions present so I'm showing you these here pause the video and try this question if we look at the zinc we can see that we start with the zinc atoms there dem and we end up with the zinc ions em2 plus in order for this to happen the zinc atom must have lost two electrons like this therefore the zinc atom has been oxidized looking at the copper we start with the copper ion Cu 2 plus and we make the copper atom Cu for this to happen the copper must have gained two electrons in other words it was reduced remember you'll find plenty more questions on oxidation and reduction in terms of electrons in my revision workbook and you can get that by clicking on the link above okay so hopefully now you should be able to explain what's meant by oxidation and reduction in terms of electrons you should then be able to identify oxidation and reduction in half equations or in symbol equations [Music]