Show that the ideal c/a ratio (height of unit cell divided by edge length) for the HCP unit cell is 1.633. (You may wish to refer to Exercise E.2 in the text page GL 1-6) Comment on the fact that real HCP metals display c/a ratios varying from 1.58 (for Be) to 1.89 (Cd). The atomic radius of HCP Mg is 0.1605 nm. Find the lattice constants, c and a, the c/a ratio and theoretical density for Mg.

The characteristics of two different types of reactions are shown below: reaction a: electrons are gained by the atoms of an element. reaction b: protons are lost by the atom of an element. which statement is true about the atoms of the elements that participate in the two reactions? their identity changes in both reaction a and reaction b. their identity changes in reaction a but not in reaction b. their identity changes in reaction b but not in reaction a. their identity remains the same in both reaction a and reaction b.