chem paper1 help

[fznkd123]

can some1 help me with this
how do we assign oxidation numbers to compounds such as HOCl and (NH4)2 SO4
iv heard this has something to do with the electro negativity but im not sure

 

[fznkd123]

and also NAClO3 ?

 

[sweetiepie]

frm where u heard ...???

 

[fznkd123]

I hav some incomplete class notes its mentioned thr but i cant figure it out

 

[sweetiepie]

okay.....

 

[xHazeMx]

can some1 help me with this
how do we assign oxidation numbers to compounds such as HOCl and (NH4)2 SO4
iv heard this has something to do with the electro negativity but im not sure

we take the oxidation number as the valency of the element in any group such as:
group 1 : +1
group 2: +2
group 3: +3
group 4: +4
group 5: -3
group 6: -2
group 7: -1
group 8: 0
now, every compound must have a total oxidation number of ZERO. for example
NaCl, Na is in group 1 having an oxidation number of +1 and Cl is in group 7 having oxidation number -1. total oxidation number is ( +1 - 1 = 0 )
some cases like in (NH4)2SO4, N has -3, H has +1, O has -2 so -2 x 4 = -8 , (NH4)2 has (-3+(4x1)) x 2 which is equal to -2. S is in group 6 so it has to be -2 but in this case O atom is more electronegative than S so S will have oxidation number of +6 inorder to get a total number of zero. remember that the total oxidation number of a compound is always zero