Crystalline Solids

Now when we use the term crystalline solids, just realize that crystalline solids are closely packed structures arranged in a highly ordered and symmetrical pattern. And with them there are three key terms you need to keep in mind first, a unit cell, we're gonna say a unit cell is the smallest and most fundamental repeating structure of a crystal lattice. And a crystal lattice itself represents identical unit cells arranged in a three dimensional space. And with that we have lattice points which are just areas within a crystal lattice which is occupied by an atom with identical surroundings. So here, if we take a look at a crystalline solid, we're going to say that the entire structure here, which looks like eight Cubes stacked with each other. This whole entire structure represents our crystal lattice. Our unit cell is one of those individual cubes. So here this would be our unit cell and the edges and points of each of those cells. That is our lattice point. So just realize when you're looking at a crystal crystal and solid, the crystalline solid can be seen as the macro view of it. And then we're going towards the lattice point which is the micro, the smallest portion of a unit cell. So just keep these terms in mind when looking at any type of crystalline solid

What is the most basic repeating structure of a crystal lattice? Remember crystal lattice? We can be seen as a crystalline solid? Which is the macro view of it? If we're talking about the repeating structures that comprise a crystalline solid, that's just our unit cell. So here option would be um answer be remember the crystalline solid is the macro view? The lightest point is just looking at one of the edges or quarters of our unit cell and then realize here that our last point is involved with the atom itself. Right? And again, our best option will be option B.

hey everyone. So when it comes to the cubic unit cell realize that there are three types of unit cell arrangements and they each possess different coordination numbers and packing efficiencies. Now, when we say coordination number, this is just the number of of neighboring atoms surrounding one atom in a crystal lattice here. If we take a view of a crystal lattice, let's have this as our atom of reference that atom we're gonna say because of this image, the coordination is equal to six. We're gonna say every atom In the Crystal Lattice is surrounded by six atoms themselves. And when we say packing efficiency, we're gonna say packing efficiency is the percentage of occupied atoms by occupied space by Adams in a unit cell. Now we're going to say the trend is, the greater the complexity then the larger the coordination number will get. And as a result of this, we're gonna have a larger packing efficiency here, we have an image of three typical types of cubic unit cells. And as we go from left to right, we can see that the cubes themselves get filled in more and more. They're becoming more and more complex with these blue regions representing additional atoms that can be comprised within a particular unit cell. So just remember as we're heading from left to right, we have an increase in complexity which will result in larger coordination numbers greater than six. And that would also result in a larger packing efficiency