Oxidation Number
It is an artificial concept to help with redox reactions. It has very little physical meaning. It is based on a set of rules that all atoms have to abide to
The oxidation state of uncombined elements is zero
- Na = 0 Cl2 = 0
The simple ions, the oxidation number of the element is the charge on the ion
- Na+ = +1, Cl- = -1
The sum of the oxidation numbers in a neutral compound is zero
- H2SO4
- H = +1
- O = -2
- Sulphur must be +6
The sum of the oxidation numbers for an ion is the charge on the ion
- Group 1 metals = +1
- Group 2 metals = +2
- Group 3 metals = +3
- Group 7 non-metals = -1
Special Rules
- Metal hydrides, H is -1
- Peroxides, O is -1
- When O is bonded to F, O is +2
Redox
- In terms of OXIDATION NUMBER
- Oxidation is increase in oxidation number
- Reduction is fall in oxidation number
Reactions of Acids are also redox
Metal + acid -> salt + hydrogen
Zn (s) + 2HCL (aq) -> ZnCl2 (aq) + H2 (g)
0 + (H=+1, Cl =-1) -> (Zn=+2, Cl = -2) +1
Worked Example:
2Na + Cl2 -> 2NaCl
0 + 0 -> (+1 / -1)
Sodium and Chlorine are both uncombined and so are 0
It is an artificial concept to help with redox reactions. It has very little physical meaning. It is based on a set of rules that all atoms have to abide to
The oxidation state of uncombined elements is zero
- Na = 0 Cl2 = 0
The simple ions, the oxidation number of the element is the charge on the ion
- Na+ = +1, Cl- = -1
The sum of the oxidation numbers in a neutral compound is zero
- H2SO4
- H = +1
- O = -2
- Sulphur must be +6
The sum of the oxidation numbers for an ion is the charge on the ion
- Group 1 metals = +1
- Group 2 metals = +2
- Group 3 metals = +3
- Group 7 non-metals = -1
Special Rules
- Metal hydrides, H is -1
- Peroxides, O is -1
- When O is bonded to F, O is +2
Redox
- In terms of OXIDATION NUMBER
- Oxidation is increase in oxidation number
- Reduction is fall in oxidation number
Reactions of Acids are also redox
Metal + acid -> salt + hydrogen
Zn (s) + 2HCL (aq) -> ZnCl2 (aq) + H2 (g)
0 + (H=+1, Cl =-1) -> (Zn=+2, Cl = -2) +1
Worked Example:
2Na + Cl2 -> 2NaCl
0 + 0 -> (+1 / -1)
Sodium and Chlorine are both uncombined and so are 0