[shelby09]

I've been trying to figure how how to write the formulas for word equations.
I'm a little confused on the subscripts.
I have an equation as an example:
Aluminum bromide + chlorine yield aluminum chloride + bromide

so far I have

Al2Br3 + 3Cl2 -> 2AlCl3 + 3Br2

The part I'm confused about is when I'm balancing the Al. I'm not sure if on the first one there should be a subscript of two. Can somebody explain and show me how to write this correctly.

[Perito]

Your Br atoms are not balanced. You have three on the left and six on the right.

First Balance The aluminum atoms. Second, balance the bromines. Finally the chlorines. The reason to do it in this way is because you can freely multiply the Br2 and Cl2 with some number to make the rest of it balance.

[bellakity]

you don't need the subscript on the aluminium bromide, it should be AlBr3

the reason for this is that Al has a valency of 3+ and Br has a valency of 1- (you can tell this by looking at the column they're in the periodic table). When compounds are formed the ions combine to give a total charge of 0. therefore, you need 3 atoms of Br and only one atom of Al, so you get AlBr3


now its easier to balance your equation:

2AlBr3 + 3Cl2 -> 2AlCl3 + 3Br2


hope that helped!