Below is the rutile structure of titania Ti light colored ox
     Below is the rutile structure of titania (Ti light colored, oxygen in dark). What is the empirical formula and how many of the molecules are in the unit cell? Show your work. What is the oxidation state of the titanium atom?   
  
  Solution
Ti=1/8*8 + 1 (at centre) = 2 atoms (since 1 atom on the corner is shared by 8 cells)
oxygen= 1/2*4 + 2= 4 atoms (face atoms are shared by 2 cells and 2 oxygen atoms are inside the cell)
therefore empirical formula= Ti2O4
oxidation state= +4

