Question

Aluminum bromide hexahydrate

How would you know its AlBr3 * 6H2O instead of just AlBr * 6H2O?

Answer 1

Al has a charge of 3, and Br has a charge of 1. it takes 3 Br for every Al.

Answer 2

Ahh Okay. So its one of those things i have to memorize?

Answer 3

yes.

Answer 4

Actually, you memorize some of it but not all of it. And if you will look at the periodic table you need not memorize any of it. Look at Al in the periodic table. It is in group 13 so the valence is 3 just as elements in group 14 are 4 etc. Get it? 3 from 13 and 4 from 14. For group 15, 16, 17, the valence is -(8-5) = -3, -(8-6)=-2 or -(8-7)=-1. So you can see Al has a valence of +3, Br has a valence of -1, compounds are zero charge; therefore, aluminum bromide is AlBr3. (The general rule is that 1, 2, 13, 14 have valences of +1, +2, +3, +4 and groups 15, 16, 17, have the difference from 8 with a negative sign added.

Answer 5

It occurred to me that I omitted groups 3,4,5,6,7,8,9,10,11,12 but those (between 2 ann 13) are done differently.

Answer 6

Ahh, now i remember my teacher telling me about it.