Problem: 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?

FREE Expert Solution

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:


F.C.=Group Number-(Bonds+Nonbonding e-)


79% (317 ratings)
View Complete Written Solution
Problem Details

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?

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Formal Charge concept. You can view video lessons to learn Formal Charge. Or if you need more Formal Charge practice, you can also practice Formal Charge practice problems.