What is the oxidation number of sulfer in each compound?
1. S-
2. SCI2-
3. SO3-
4. H2S-
5. S2CI2-
6. H2SO4-

Oxidation number of sulphur in S is 0, in SCl2 is +2, in SO3 is +6, in H2S is - 2, in S2Cl2 is +1, in H2SO4 is +6.

Oxidation number is the numeric representation of the charge of the particular atom in a compound assuming the compound is 100% ionic in character. This oxidation number is calculated based on the electronegativity of the participating atoms and the valemct of the atoms.

In S, there are no other atoms except sulphur. So its an elemental atom and elemental atoms have oxidation number of 0.

In SCl2, chlorine is more electronegative than sulphur, so chlorine is given - 1 based on its valency and electronegativity. So sulphur will have the oxidation number of +2.

In SO3, oxygen is more electronegative than sulphur, so given - 2 based on its valency and electronegativity. So sulphur will be +6.

In H2S, hydrogen is electropositive than sulphur, so given +1. So the oxidation number of sulphur will be - 2.

In S2Cl2, chlorine is more electronegative than sulphur, so chlorine is given - 1 based on its valency and electronegativity. So sulphur will have the oxidation number of +1.

In H2SO4, hydrogen is electropositive than sulphur, so given +1 and oxygen is more electronegative than sulphur, so given - 2. So oxidation number of sulphur will be +6.

it is stable as it is in group 0 which have full outer shells of electrons