An element exists in two allotropic forms. One form is CCP and the other form is HCP arrangement of — Solid State Chemistry Question

💡 Solution & Explanation

Both CCP and HCP have an identical optimal packing efficiency of 74% (meaning 26% unoccupied space) and a coordination number of 12. Since the atomic radius and mass are the same, their density is the same. The perpendicular distance between consecutive close-packed layers is equivalent in both structures ($2r\sqrt{2/3}$). Therefore, correct answer is A,B,C,D.