To remember the difference between covalent network solids, atomic network solids, and amorphous solids think about in in dimensions, which they are.

3D= Diamond a three dimensional solid (covalent-atomic) 2D = Graphite, you draw 2D figures with a graphite pencil (covalent- molecular) 1D = No dimension like glass, no order

Metals conduct beaus of delocalized electrons. Band theory is similar to thinking about molecular orbitals the concept from chem 1. When two atoms bond their atomic orbital mix and form molecular orbitals. But in band theory it is on a much larger scale 10^23 atoms or avagadros number. Insulators have big gaps in the connection band and semi conductors have small gaps in the connective bands.

We can not measure lattice energy as it is the energy released when gas ions can together to form a solid. It is calculated indirectly using Hess's Law applied to ionic solids. We break it down into key steps: Sublimation, ionization, bond dissociation, electron affinity, and formation. Remember these key steps

Relating to unit cells, the ionic structures depend on the cation vs anion size. For example, for CsCl it is primitive cubic, Cs+ in the center was Cl- on the corners. NaCl is FCC with Na+ in the 8 holes, Cl- ions are much bigger than Na+ so sodium fits into the holes left by chlorine. CaF2 is also FCC with tetrahedral holes Ca2+ fits into the gaps left by Flourine.

In Crystal defects there are either imperfections that change crystal properties by swapping the atom (substitutional) or squeeze in an atom (interstitial). Example of substitutional: Brass. Cu + Zn. Copper atoms are replaced by zinc atoms, they are similar size so they substitute to make a stronger mental.

Example of Interstitial defects: Steel. Smaller carbon atoms squeeze into holes between iron atoms. This forms steel and makes it harder and stronger than iron alone.

Get side length from the density and geometry formulas to obtain the radius. Density to volume to edge length to radius