Chemistry Forum

Hi guys, can someone help me figure out what each of the four Sulfur's oxidation number for H₂S₄ is? I know H is 1 and S is 6 but I don't get how you find the individual oxidation numbers for Sulfur..

Generally Bonds between the same type of Element are 0.
So we have a chain HSSSSH. Hydrogen is +1 and the first and fourth sulfur is -1. The other two 0.

I see, thank you!

skycracker00 wrote: ↑Thu Oct 28, 2021 11:50 pm I see, thank you!

ChenBeier is spot on correct!
But here's some rules of thumb and tips regarding oxidation numbers that I found helpful when I was learning way back when...I still use these today when tutoring/teaching chemistry to others!

Rules for assigning oxidation numbers:

• The oxidation number of a free element is always 0.

• The oxidation number of a monatomic ion equals the charge of the ion.

• Fluorine in compounds is always assigned an oxidation number of -1.

• The alkali metals (group I) always have an oxidation number of +1.

• The alkaline earth metals (group II) are always assigned an oxidation number of +2.

• Oxygen almost always has an oxidation number of -2, except in peroxides (H₂O₂) where it is -1 and in compounds with fluorine (OF₂) where it is +2.

• Hydrogen has an oxidation number of +1 when combined with non-metals, but it has an oxidation number of -1 when combined with metals.

• The algebraic sum of the oxidation numbers of elements in a compound is zero.

• The algebraic sum of the oxidation states in an ion is equal to the charge on the ion.

Assigning oxidation numbers to organic compounds:
The oxidation state of any chemically bonded carbon may be assigned by adding -1 for each bond to more electropositive atom (H, Na, Ca, B) and +1 for each bond to more electronegative atom (O, Cl, N, P), and 0 for each carbon atom bonded directly to the carbon of interest.
For example:

• propene: CH₃-CH=CH₂

• lauric acid: CH₃(CH₂)₁₀COOH

• di-tert-butyl peroxide: (CH₃)₃COOC(CH₃)₃

• di-isopropyl ether: (CH₃)₂CH-O-CH(CH₃)₂

• dibenzyl sulfide: (C₆H₅CH₂)₂S

• cysteine: HO₂CCH(NH₂)CH₂SH

Good summary.