Ionic crystals are hard because of tight packing lattices, say, the positive and negative ions are strongly attached among themselves.
<span>some elements would be Beryllium, Barium, Magnesium, and Strontium</span>
Henry Mosely reorganized Mendeleev's periodic table so it would be in order of atomic number (number of protons) instead of in order by atomic mass. (I don't know the answer to the other 2 questions I apologize)
I don’t know but sorryyyyyy
