[Music] hi and welcome back to free science lessons by the end of this video you should be able to describe metallic bonding you should then be able to describe and explain the properties of pure metals and Alloys now metals are very important in chemistry I'm showing you here a gold bar which is essentially pure gold and a guitar string which is an alloy we'll be looking at what's meant by an alloy later in this video so let's stop by taking a closer look at Metals in previous videos we've seen that atoms become stable by achieving a full outer energy level when a metal atom reacts with a non-metal atom we see ionic bonding and when two non-metal atoms react we see Cove valent bonding so let's look at bonding in metals Metals consist of a giant structure of atoms arranged in regular layers and I'm showing you that here in metal the electrons in the outer energy level of each atom are delocalized so let's take a look at what that means I'm showing you here atoms of the metal lithium lithium atoms have three protons in their nucleus and three electrons in their energy levels now the key fact is that in metals the outer electrons are not attached to any individual atom in fact the outer electrons are free to move through the whole structure scientists call these Deo alized electrons and I'm showing you these here now we can call this a c of delocalized electrons and it's often shown like this because each metal atom has lost its Auto electron we now refer to them as positive metal ions but remember that this is not ionic bonding this is metallic bonding now between the Sea of delocalized negative electrons and the positive metal ions we have a strong electrostatic attraction and electrostatic attraction is an attraction between a positive object and a negative object the electrostatic attraction in metals is called a metallic bond and metallic bonds are strong now metals have high melting and boiling points in order to melt a metal we have to break the strong metallic bonds this requires a great deal of energy and this explains why metals have high melting and boiling points metals are also excellent conductors of heat and electricity that's because the localized electrons can move because electrons are charged these moving electrons can carry an electric current also the moving electrons can carry thermal energy which allows metals to conduct heat now another property of metals is that metals can be bent and shaped that's because in metals the layers of atoms can slide over each other like this now this presents a problem some pure metals are not hard enough to be useful this includes copper gold iron and aluminium so we need to make these Metals harder and to do that we make an alloy an alloy is a mixture of metals in an alloy the different sizes of atoms distorts the layers this makes it more difficult for the layers to slide over each other and this means that allies are harder than pure Metals you'll find plenty of questions on this topic in my vision workbook which you can get by clicking on the link above [Music]