[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 covalent bonding in water ammonia and methane in the last video we started looking at Cove valent bonding we saw that calent bonding takes place between non-metal elements and remember that a coent bond is a shared pair of electrons a Cove valent bond is a strong bond we saw Cove valent bonding in hydrogen chlorine and hydrogen chloride and you'll notice that each of these molecules have two atoms joined by a single calent bond in this video we're going to look at molecules containing several atoms these molecules are water ammonia and methane and you could be asked about these molecules in your exam we're going to start with water okay water has a formula H2O this tells us that a water molecule contains two atoms of hydrogen and one atom of oxygen I'm showing you an atom of oxygen here oxygen has eight electrons in total there are two electrons in the first energy level and six electrons in the outer energy level notice that I'm only showing the outer energy level and that's because only the outer energy level is involved in chemical bonding here's an atom of hydrogen and remember that hydrogen only has one electron in total now the formula for water tells us that the water molecule contains two hydrogen atoms so here's the second hydrogen atom now both hydrogen atoms require one more electron to achieve a full outer energy level however the oxygen atom requires two more electrons we can achieve this by overlapping the outter energy levels for the hydrogen atoms and oxygen atom like this by sharing electrons both the hydrogen atoms and the oxygen atom have a full outer energy level remember that a shared pair of electrons is a calent bond so the water molecule contains two calent bonds here's the dot and cross diagram for the water molecule and here's the stick diagram and remember that in the stick diagram a single line represents a single Cove valent Bond okay the next calent molecule we're looking at is called ammonia ammonia has a formula NH3 this tells us that an ammonia molecule contains one atom of nitrogen and three atoms of hydrogen I'm showing you an atom of nitrogen here nitrogen has five electrons and its outer energy level hydrogen atoms only have one electron and I'm showing the three hydrogen atoms here I'd like you to draw The Cove valent bonding in the ammonia molecule that includes the energy level diagram the dot and cross diagram and the stick diagram so positive video now and try this yourself okay here's the energy level diagram for ammonia we can see that a molecule of ammonia has three calent bonds by sharing electrons the nitrogen atom and the hydrogen atoms have each achieved a full outer energy level here are the dot and cross diagram and the stick diagram for ammonia okay our final calent molecule is methane which has a formula CH4 this tells us that a methane molecule contains one atom of carbon and four atoms of hydrogen I'm showing you an atom of carbon here carbon has four electrons in its outer energy level here are the four hydrogen atoms and remember that hydrogen only has one electron I'd like you to draw The Cove valent bonding in the methane molecule so pause the video now and try this yourself okay here's the energy level diagram for methane we can see that a molecule of methane has Four Cove valent bonds and now the carbon atom and the hydrogen atoms all have full outer energy levels here are the dot and cross diagram and the stick diagram from methane you'll find plenty of questions on this topic in my vision workbook which you can get by clicking on the link above [Music] above