 Ionic solids have a definite crystalline structure. In this model, you see a sodium and chlorine atom, and they're attached to opposite types of atoms. So if this is sodium, that's a chlorine, that's a chlorine, that's a chlorine. If you look inside here, that is attached to six atoms of the opposite type. If you hammer on this, and this slides down to here, then the white ones, they're going to repel each other because they're electrostatic charges. This would be a positive and a positive, and that would be a negative and a negative. So if you push that down, they're going to repel and the whole thing breaks. This is another example of an ionic compound. But one of the ions is formed by covalent molecules. This is a carbonate, carbon and three oxygens, CO3, 2 minus. And this is a calcium. So this is calcite, or calcium carbonate. So you see here is a calcium here, and to that calcium is attracted 1, 2, 3, 4, 5, and then there would be another one out this way. So that would be attracted to six negative ions.