Hydride and Oxidation state...

[johnwandering]

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I was under the assumption that an atom losing an electron to a more electronegative gives it a (+) and vice versa


However, what is the deal with Hydride?
for example, LiAlH4
Why is the oxidation state +3?

Li is less Electronegative that Al= -1
The extra electrons in H that Al didn't have before= -4
Shouldn't it be -5?



Can someone please tell me how you can add a negatively charged Hydride to an atom and end up causing a Positive oxidation state???

 

[PiBond]

I was under the assumption that an atom losing an electron to a more electronegative gives it a (+) and vice versa


However, what is the deal with Hydride?
for example, LiAlH4
Why is the oxidation state +3?

Li is less Electronegative that Al= -1
The extra electrons in H that Al didn't have before= -4
Shouldn't it be -5?



Can someone please tell me how you can add a negatively charged Hydride to an atom and end up causing a Positive oxidation state???

the H's actually have a negative oxidation state and thus -4 and the +1 for lithium gives the Al a +3 charge. when LiAlH4 reacts as a reducing agent the H's actually act as a nucleophile because the have the electrons. it's weird, i know