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. (c) Based on electronegativity differences, predict the identity of the polyatomic anion. Draw a Lewis structure for this ion.

Video transcript

Hi everyone here we have a question telling us that sodium Borough hydride has Covalin bonds that bind poly atomic and ions together. It also has ionic bonds. And we want to make a prediction on the poly atomic and ions identity based on variations of the electro negativity. So we know that polly atomic ions are held together by Covalin bonds. So let's look at some of the possible Covalin bonds for sodium Borough hydride. We have sodium and hydrogen or we have boron and hydrogen. So let's look at our difference in electro negativity. So sodium hydrogen electro negativity ease Equals the absolute value of 0.9 -2.2, which is -1.3. And then we have boron and hydrogen electro negativity ease. And that equals the absolute value of 2 -2.2 Or 2.2, Which equals 0.2. So we want to find the smaller electro negative difference which in this case is four on hydrogen. The smaller electro negative Prince means that it is more Covalin and because it is more Covalin that is more likely that it is the poly atomic ion. So our poly atomic ion is B. H. Four. And that is our final answer. Thank you for watching. Bye.