[Music] hi and welcome back to free science lessons by the end of this video you should be able to describe how electrons are transferred during ionic bonding you should then be able to draw Dot and cross diagrams to show ionic bonding we saw in a previous video that electrons exist in energy levels or shells I'm showing you here the electrons in an atom of argon and Aron is in group zero which is also called the noble gases remember that the first energy level can hold a maximum of two electrons and the second energy level can hold a maximum of eight electrons the third energy level can also hold eight electrons before the fourth energy level starts filling now all of the noble gases in group Zero have a full outer energy level scientists say that a full outer energy level is stable and because of this the group zero noble gases are unreactive in this video we're looking at ionic bonding let's start by looking at some key facts that you need to learn firstly elements react in order to achieve a full outer energy level and by doing this they achieve this stable electronic structure of a noble gas in other words a full outer energy level looking at the periodic table we can see that metals are on the left hand side and non-metals are found on the right lots of reactions in chemistry involve a metal reacting with a non-metal and when a metal and a non-metal react ionic bonding takes place let's start by looking at ionic bonding between the group one metal lithium and the group seven non-metal Florine I'm showing you here an atom of lithium as you can see a lithium atom has three electrons there are two electrons in the first energy level and then one electron in the outer energy level and remember that electrons have a negative charge lithium atoms also have three positive protons in the nucleus now because there are the same number of protons and electrons the charges cancel so an atom of lithium has no overall charge here's an atom of Florine a fline atom has nine electrons there are two electrons in the first energy level and then seven electrons in the outer energy level fline atoms also have nine positive protons in the nucleus again because there are the same numbers of protons and electrons the charges cancel so an atom of Florine has no overall charge now I'm using dots to show the electrons on the lithium atom and Crosses to show the electrons on the fline atom but remember that all of the electrons are the same whether they're shown by dots or by crosses we can see that neither lithium nor fline has a full outer energy level when we react lithium with Florine the lithium atom loses its outer electron and this electron is gained by the fline atom like this now both the lithium atom and the fline atom have full outer energy levels looking again at the lithium atom we can see that it still contains three positive protons however now the lithium atom only has two negative electrons this means that lithium now has an overall one positive charge We Now call this a lithium ion and an ion is an atom with an overall charge the fline atom still contains nine positive protons however the fline atom now has 10 negative electrons this means that fline now has an overall one negative charge We Now call this a fluide ion both the lithium ion and the fluide ion now have a full outer energy level in other words they both have the stable electronic structure of a noble gas so remember that during aonic bonding group one metals lose one electron forming a one positive ion and group seven non-metals gain one electron forming a one negative ion both ions now have a full outer energy level in other words the stable electronic structure of a group zero noble gas okay now we often see exam questions on this topic and I'm showing you a typical exam question here this shows the reaction between the group one metal sodium and the group seven non-metal chlorine the question asks us us to describe what's happening in this reaction for three marks now this Dot and cross diagram only shows the outer energy levels and that's because only the outer energy levels are involved in the reaction so we would say that one electron passes from the sodium atom to the chlorine atom and both atoms achieve a full outer energy level you'll find plenty of questions on this topic in my vision workbook which you can get by clicking on the link above [Music]