A major challenge in implementing the "hydrogen economy" is finding a safe, lightweight, and compact way of storing hydrogen for use as a fuel. The hydrides of light metals are attractive for hydrogen storage because they can store a high weight percentage of hydrogen in a small volume. For example, NaAlH4 can release 5.6% of its mass as H2 upon decomposing to NaH(s), Al(s), and H2 (g). NaAlH4 possesses both covalent bonds, which hold polyatomic anions together, and ionic bonds.
(a) Write a balanced equation for the decomposition of NaAlH4.
(b) Which element in NaAlH4 is the most electronegative? Which one is the least electronegative?
(c) Based on electro negativity differences, what do you think is the identity of the polyatomic anion? Draw a Lewis structure for this ion.