We’re being asked to determine the formal charge of hydrogen in the polyatomic ion in NaAlH4.
To do so, we need to do the following steps:
Step 1: Determine the polyatomic ion.
Step 2: Determine the central atom in this molecule.
Step 3: Calculate the total number of valence electrons present.
Step 4: Draw the Lewis structure for the molecule.
Step 5: Calculate the formal charge for the indicated atom.
Recall that the formula for the formal charge is:
A major challenge in implementing the “hydrogen economy” is finding a safe, lightweight, and compact way of storing hydrogen for use as 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.
What is the formal charge on hydrogen in the polyatomic ion?
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