AlH3

Ana36

Please excuse my phrasing, have not quite grasped the whole chemistry language yet as I am just a beginner

When bonding atoms, there are generally 8 electrons...eg. Na2S, CaCl2 etc all have 8 electrons...got that...however...

Could somebody please explain why this doesn't seem to be as straight forward with Aluminium Hydride.

Hope my question makes sense.
Thanks, much appreciated.

Well, I could be totally off the mark here, but seeing as you haven't gotten any other replies, I'll throw this out there.

If I understand your question correctly, you've established that in CaCl2, Ca gets rid of two minus charges and each Cl acquires one minus charge, resulting in a shared total of 8 valence electrons each. So you've looked at AlH3 and you see a Al which has 3 valence electrons and H which has one, and you've added the three H electrons to Al and it only makes up 6 instead of 8?

If that's the problem, then it's just that you're looking at it back to front. Al doesn't fill it's valence shell with electrons by gaining electrons, instead each H gains one electron, so the Al loses three electrons, thereby making the 8 it has left in the next lower level it's valence electrons. H only needs two electrons to fill it's valence shell.

Sorry if that's not clear or didn't catch your actual question, plus as it usually exists in a complex it's not really as "you give an electron/you lose an electron" as I'm making out, but if I've steered you wrong I'm sorry!

Ana36

true-or-false wrote: »

Well, I could be totally off the mark here, but seeing as you haven't gotten any other replies, I'll throw this out there.

If I understand your question correctly, you've established that in CaCl2, Ca gets rid of two minus charges and each Cl acquires one minus charge, resulting in a shared total of 8 valence electrons each. So you've looked at AlH3 and you see a Al which has 3 valence electrons and H which has one, and you've added the three H electrons to Al and it only makes up 6 instead of 8?

If that's the problem, then it's just that you're looking at it back to front. Al doesn't fill it's valence shell with electrons by gaining electrons, instead each H gains one electron, so the Al loses three electrons, thereby making the 8 it has left in the next lower level it's valence electrons. H only needs two electrons to fill it's valence shell.

Sorry if that's not clear or didn't catch your actual question, plus as it usually exists in a complex it's not really as "you give an electron/you lose an electron" as I'm making out, but if I've steered you wrong I'm sorry!

Thanks for your answer,
I eventually got it..wasn't taking into consideration that hydrogen only needs 2 electrons to fill its valence shell! Doh!