Oxidation States

Unit 8

1

Oxidation States

2

Goal: Identify if a reaction is a redox reaction

Oxidation State: The charge that an atom appears to haveCommon sense usually prevails when assigning oxidation states

Rules for assigning oxidation state1. The oxidation number of ANY element in its most stable form is ALWAYS 0.

Examples: Fe(s), O2, Cl2, F2, N2, C(s)2. If monoatomic ions appear in the equation (e.g. Na+), the charge is the oxidation

state.3. Group IA = +1 and Group IIA = +2.

4. Halogens are usually -1.5. Oxygen is usually -2. Exceptions: O2 = 0 and H2O2 = -1.

6. Hydrogen is usually +1. Exceptions: H2 = 0 and when bonded to a metal (NaH) = -1.7. Binary Compounds: most electronegative has its charge as an anion (e.g. F = -1, O =

-2, etc.) and cation balances the charge

Oxidation State

3

Rules for assigning oxidation state1. The oxidation number of ANY element in its most stable form is ALWAYS 0.

Examples: Fe(s), O2, Cl2, F2, N2, C(s)2. If monoatomic ions appear in the equation (e.g. Na+), the charge is the oxidation

state.3. Group IA = +1 and Group IIA = +2.

4. Halogens are usually -1.5. Oxygen is usually -2. Exceptions: O2 = 0 and H2O2 = -1.

6. Hydrogen is usually +1. Exceptions: H2 = 0 and when bonded to a metal (NaH) = -1.7. Binary Compounds: most electronegative has its charge as an anion (e.g. F = -1, O =

-2, etc.) and cation balances the charge

Cl2 FeH2 CH2O NH3 NH4+

Oxidation State

4

Rules for assigning oxidation state1. The oxidation number of ANY element in its most stable form is ALWAYS 0.

Examples: Fe(s), O2, Cl2, F2, N2, C(s)2. If monoatomic ions appear in the equation (e.g. Na+), the charge is the oxidation

state.3. Group IA = +1 and Group IIA = +2.

4. Halogens are usually -1.5. Oxygen is usually -2. Exceptions: O2 = 0 and H2O2 = -1.

6. Hydrogen is usually +1. Exceptions: H2 = 0 and when bonded to a metal (NaH) = -1.7. Binary Compounds: most electronegative has its charge as an anion (e.g. F = -1, O =

-2, etc.) and cation balances the charge

NO2- NO3

- CH4 CCl4

Oxidation State

5

Rules for assigning oxidation state1. The oxidation number of ANY element in its most stable form is ALWAYS 0.

Examples: Fe(s), O2, Cl2, F2, N2, C(s)2. If monoatomic ions appear in the equation (e.g. Na+), the charge is the oxidation

state.3. Group IA = +1 and Group IIA = +2.

4. Halogens are usually -1.5. Oxygen is usually -2. Exceptions: O2 = 0 and H2O2 = -1.

6. Hydrogen is usually +1. Exceptions: H2 = 0 and when bonded to a metal (NaH) = -1.7. Binary Compounds: most electronegative has its charge as an anion (e.g. F = -1, O =

-2, etc.) and cation balances the charge

Cr2O72- CrO4

2-