Thoria or thorium dioxide can be described as an FCC lattice with a basis of Th (0, 0, 0) and O (1/4, 1/4, 1/4) and O (1/4, 1/4, 3/4). Thorium and thorium dioxide are radioactive materials. Thorium dioxide is commonly used in tungsten electrodes for arc welding. Thoria improves the high temperature properties of the electrodes
and promotes emission of electrons from the electrode tip.
(a) How many atoms of each type are there in the conventional unit cell of thorium dioxide?
(b) Is this consistent with the chemical formula of thorium dioxide? Explain.
(c) What is the coordination number (number of nearest neighbors) for each Th atom?
(d) What is the coordination number (number of nearest neighbors) for each O atom?
(e) What type of interstitial site do the oxygen atoms occupy?