Good day, great tense. In today's lesson we're going to be looking at dissolving our inexilates, but what is an ionic solid? Now, in the last lesson we learnt about electro negativity and we realised that electro negativity was a measure of how strongly an atom holds onto its own electrons and attracts other electrons to it. Now, if the electro negativity is different between the atoms and the molecule is greater than 1.9, we said that the molecule has ionic bonding. That means that there are very strong electrolytic forces holding the atoms together in the molecule. Let's take an example. Let's look at sodium chloride which is table salt. Again, we've got this beautiful periodic table which has got all the electro negativities. Now, sodium chloride is made up of sodium and if we look every year we can see that the electro negativity of sodium is 0.9 which means it doesn't hold onto its electrons very well at all and chlorine has over there an electro negativity of 3 which means that not only hold onto its electrons very well but it also will attract electrons from other atoms. So electro negativity difference is going to be 2.1 which means that it's ionic. So electro negativity is going to be very strongly bonded together. Now, let's see what happens when we add an ionic substance to water. Sodium chloride crystals are held together by attractive forces between the positively charged sodium and negatively charged chloride ions. When a crystal of sodium chloride is placed into water, the hydrogen ends of polar water molecules attract the negatively charged chloride ions and gradually surround. Okay, so I know that he's going to tell us this but just watch here. Yari are water molecules and Yari is the oxygen and these are hydrogens and they are surrounding this but the hydrogens are positive, right? So it's carry on. Likewise, the oxygen ends of water molecules are attracted to and surround the positively charged sodium ions. The hydrated ions drift away into the solution allowing new water molecules to surround newly exposed ions. Gradually, the entire crystal dissociates into solution. Right, so now let's just summarize what we actually learned to that. When we have an ionic substance and it's added to water, the forces of attraction between the polar water molecules and the positive negative and positive and negative ions occur. Right, these forces of attraction are intermolecular forces. That means that they are forces between molecules. Intermolecular is not within the molecule but between the molecules. These are ion dipole forces. The dipole is the water because it's a polar molecule and the ions are, for example, in this case, the chloride ions and the sodium ions and they're weak temporary forces. So we saw in that little video that the basically what would happen is that water molecule would come along. The intermolecular force will overcome the electrostatic forces between the chlorine and sodium and they will pull the chloride ion away and similarly, the water molecules that with the oxygen end facing it will pull the sodium ions apart. So basically what happens is your sodium and chloride crystals are pulled apart. Then what happens is each ion is surrounded by water molecules. So you've got here, you can see here is your negative chloride ion and it's surrounded by the water molecules but no time. The positive hydrogen atoms are facing the negative chloride ion. Similarly, here is a positive sodium ion and this time the negative oxygen atoms are facing them. So when we're talking about dissolving, we're actually made up of two processes. The first is dissolution and the second is hydration. So the dissolution was a process in which the ionic substance breaks down into ions. So that's the point where the water molecules are pulling the chloride and sodium ions off the molecule, the big crystal. And then you've got hydration and the hydrogen and then you've got hydration and this is the process in which the catapas, the positive ions and the anions, the negative ions, becomes surrounded by water molecules. Okay, so when it becomes surrounded by the water molecules, that's hydration. So if we had to write that as an equation, we would say that sodium chloride which is a solid but in this case it's been dissolved into water, breaks down into sodium ions and chloride ions. So it would be NACL, the solid has been broken down to NAPLAS but now it's acquires because it's been dissolved into water and chloride ions and again it's acquires because it's been dissolved into water. So now you know how it goes about that we've got ionic solutions and how the ionic solution is dissolved in the water. Please remember the two processes and learning properly. Thank you very much great times, hope you have a great day.