now the most fundamental distinction between solids is that they can be classified as either crystalline or amorphous solids. Now we say crystal and solid, we're going to say here that atoms ions or molecules that have highly ordered uh arrangements throughout. And amorphous solids are particles that are randomly arranged throughout with no discernible pattern. Now when we say crystalline solids we're referring to as ionic solids, molecular solids, co violent network solids and metals. Now here we're going to say for ionic solids, the smallest unit is the ionic part and that's because it's electric electrostatic forces is the attraction between a positive ion and a negative ion. Remember we know the definition of ionic compounds is a cat eye on connected to an an eye on that. Can I um can be a metal or ammonium ion, that an ion is just some non metals. Now we can say here also their properties is that ionic solids tend to be brittle and yet hard and we're gonna stay here that they have high melting points. A good example is if we're looking at solid sodium chloride for Ariana compound, molecular solids, not molecular solids. Their smallest student is the molecule. Their electrostatic force are the inter molecular forces. We're gonna stay here that they have soft textures to them we're going to say they have low to moderate melting points. Good example of a molecular solids or molecular solid that we can think of. We could think of ice which is just hte tool solid Covalin network. Now some of you may not know what this is. Covalin networks, their smallest student is the atoms, they are co valent bonds for their electrostatic force. Now, if you want to understand the hardest materials in nature, you're referring to the Covalin Network solids. They have very hard textures and they have very high melting points even higher than our ionic solids. A great example, one of the hardest natural substances in nature diamonds remember diamonds are just a form of carbon, so carbon diamond but that's not the only form that carbon can take with. The nature could also take carbon graphite as well. Now medals, medals of course are composed of metal atoms were going to say here that we're dealing with metallic bonds and that's just the pooling of electrons on the surface of your metal. We're gonna say they can be lustrous, which means that they are shiny, they can be from soft textures with sodium hard textures to like titanium. We're gonna say they also have high melting points. So here an example is the ones we gave sodium or titanium. Finally, we have our amorphous solids which is different from all these other crystalline solids here they are composed of atoms, ions, molecules or will refer to as polymers when we say polymers, we're talking about different forms of plastics because they don't have a discernible pattern, they kind of resemble some of the crystalline solids we mentioned up above. So that means the electrostatic force could be any of the ones mentioned above because of their weird nature and composition. They tend to not have a distinct melting point. And what's really weird about them is that they're solids but they're able to flow. So that's not a normal thing. The ability to flow is usually reserved for salt for liquids and gasses, not solids. Now, a great example here you can say is glass war tar. So tar the material that we use on roads. So that's an example of an amorphous solid. And if you can understand what our looks like black sticky stuff, it's able to flow. All right. So, these are the different types of crystalline solids and how they're different from an amorphous solid.