People have answered most of your questions. However, I want to address the issue of crystal sizes. Sorry, I cannot type in Thai so please bear with me.
There is no standard that you can say a crystal of this compound has to be this big or another compound has to be that big, really. For example, recently a group of U.S. scientists have grown a very large crystal of a salt (it is really huge) so they can use it in their spectroscopic studies. With the same salt, you may just get a tiny crystal if your conditions are different. Like the above comments, it all depends on the crystal growth conditions that you choose. So to expect that a NaCl crystal has to have a particular size is not reasonable since it depends on the amount of NaCl you have in the solution, the time for which you allow the crystals to grow, etc.
However, to analyze crystal shapes or morphologies can be more systametically expected or studied. For example, you can expect that a crystal of NaCl should have a cubic shape. I am not going to go into much detail but the shape of the crystals obtained is related to the most stable crystallographic space group of your crystals grown under a particular set of conditions. It is noted that the same compound can even crystalize in different crystallographic space groups.
I really do hope you may find this helpful.
a science major
24 พ.ย. 45 14:10:05