Writing out chemical equations

[Ryuk1990]

Homework Statement

Write a balanced equation for:

1. the reaction of chromium with sulfur

2. the reaction of bismuth with oxygen

Homework Equations

Chromium is a transition metal and sulfur has a 2- charge.

The Attempt at a Solution

For the first one, I'm thinking that since sulfur has a 2- then chromium must have a 2+ charge so it would form a product of CrS. I thought it would just be Cr + S ----> CrS

That's before balancing of course but that's not the answer either. It's supposed to be Cr + S ----> Cr₂S₃ (before balancing)

Why are there subscripts?

The second one makes absolutely no sense to me because O is 2- and Bi is I believe 3-.

 

[Fightfish]

Chromium is most commonly found in the +3 oxidation state.

Have you heard of covalent bonding?

Also, the way in which you refer to O as being "2-" etc. is incorrect. An atom is electrically neutral. What you actually mean is that oxygen tends to form O^2- ions.

 

[Borek]

Bismuth - like chromium - likes +3, Bi³⁺.