solve all question ( 3 & 4 ) plz

3-Arrange the following ions in order of decreasing size: Br,I,Mg2+,Ca2+ 4-Fill in blanks a) In a face centred cubic (fcc) arrangement, the number of atoms per unit cell is b)In salts of formula MX2 : if the coordination number of M is 6 then the coordination number of X is c) is the enthalpy change in the formation of an ionic solid from gaseous ions. d)Magnesium reacts with nitrogen to form an ionic solid. The correct formula for this solid is e) The coordination number for a metal atom in a body centered cubic arrangement is f) The coordination number for a metal atom in a cubic closest packed arrangement is g) In a solid lattice the cation left its usual lattice site and is located at an interstitial position, the lattice defect is