[Music] hi and welcome back to free science lessons by the end of this video you should be able to describe how electrons are shared in Cove valent bonding you should then be able to draw diagrams to show Cove valent bonding in hydrogen chlorine and hydrogen chloride and I should point out that these molecules are required in the specification we've already seen that ionic bonding happens when a metal reacts with a metal remember that the outer electrons are transferred from the metal atom to the non-metal atom ionic bonding produces ions which are atoms with an overall charge and ions have this stable electronic structure of a noble gas in other words a full outer energy level so in this video we're looking at what happens when non-metal atoms bond together this is called Co valent bonding we're going to start by looking at a very simple calent molecule which is the hydrogen molecule H2 so what does this formula tell us well it tells us that we have two hydrogen atoms bonded together here's hydrogen on the periodic table and we can see that hydrogen is a non-metal element I'm showing you here an atom of hydrogen and you can see that hydrogen only has one electron now the first energy level can hold a maximum of two electrons so this hydrogen atom requires one more electron to achieve a full outer energy level in the case of a hydrogen molecule it achieves this by bonding with another hydrogen atom so I'm showing you here a second atom of hydrogen for this hydrogen atom I'm showing the electron as a cross rather than a DOT however you need to remember that dots and Crosses both show an electron so now the two hydrogen atoms overlap their energy levels and they share their electrons like this now you can see that both hydrogen atoms have two electrons in other words both atoms have achieved a full outer energy level just like a group zero noble gas by sharing a pair of electrons the hydrogen atoms have formed a single Cove valent Bond and you need to remember that a calent bond is a strong bond now scientists call a diagram like this an energy level diagram and you could be asked to complete one of these in your exam another way of representing this is called a DOT and cross diagram remember that a DOT and cross diagram only shows the electrons in the outer energy level so this shows the dot and cross diagram for the hydrogen molecule and again you could see this in your exam now we can represent calent molecules in an even simpler way and this is called a stick diagram so here's the stick diagram for the hydrogen molecule the line represents the single Cove valent bond in other words the shared pair of electrons you'll see stick diagrams a lot in chemistry okay let's look now at a slightly more complicated molecule this is the chlorine molecule cl2 here's chlorine in the periodic table and you can see that chlorine is a non-metal I'm showing you here two atoms of chlorine and notice that I've only drawn the outer energy levels that's because only the outer energy levels are involved in chemical bonding each atom of chlorine has 17 electrons so it has seven electrons in its outer energy level and we know that because chlorine is in group seven each atom of chlorine requires one more electron to achieve a full outer energy level they can do this by overlapping their outer energy levels and forming a single coent Bond like this so this is the energy level diagram for the chlorine molecule cl2 here are the dot and cross diagram and stick diagram for the chlorine molecule okay we're going to look at one final small calent molecule this is called hydrogen chloride which has the formula HCL as we've seen before both hydrogen and chlorine are non-metals so hydrogen chloride is a calent molecule as we've seen a hydrogen atom only has one electron a chlorine atom has seven electrons in its outer energy level I'd like to draw The Cove valent bonding in the hydrogen chloride molecule so pause the video now and try this yourself okay both atoms require one extra electron to achieve a full outer energy level and they do this by overlapping their outer energy levels like this here are the dot and cross diagram and the stick diagram for hydrogen chloride you'll find plenty of questions on this topic in my vision workbook which you can get by clicking on the link [Music] above [Music]