-1 for each Cl
+3 for N
The oxidation number of N in NCl3 is +3. This is because the oxidation number of Cl is -1, and there are three Cl atoms in NCl3, so the overall charge must be balanced by N having an oxidation number of +3.
The oxidation number of Cl in NCl3 is -1. Nitrogen typically has an oxidation number of -3 in nitrogen-containing compounds, so the overall charge of NCl3 must be 0, making the oxidation number of Cl -1.
In KMnO4, Mn has an oxidation number of +7, KNO2 has N with an oxidation number of +3, and H2SO4 has S with an oxidation number of +6. In MnSO4, Mn has an oxidation number of +2, H2O has O with an oxidation number of -2, KNO3 has N with an oxidation number of +5, and K2SO4 has S with an oxidation number of +6.
The oxidation number of hydrogen in NH3 is +1, and the oxidation number of nitrogen is -3. This is because hydrogen typically has an oxidation number of +1 and in compounds, nitrogen usually has an oxidation number of -3.
-2
The oxidation number of N in NCl3 is +3. This is because the oxidation number of Cl is -1, and there are three Cl atoms in NCl3, so the overall charge must be balanced by N having an oxidation number of +3.
The oxidation number of Cl in NCl3 is -1. Nitrogen typically has an oxidation number of -3 in nitrogen-containing compounds, so the overall charge of NCl3 must be 0, making the oxidation number of Cl -1.
In KMnO4, Mn has an oxidation number of +7, KNO2 has N with an oxidation number of +3, and H2SO4 has S with an oxidation number of +6. In MnSO4, Mn has an oxidation number of +2, H2O has O with an oxidation number of -2, KNO3 has N with an oxidation number of +5, and K2SO4 has S with an oxidation number of +6.
The oxidation number of hydrogen in NH3 is +1, and the oxidation number of nitrogen is -3. This is because hydrogen typically has an oxidation number of +1 and in compounds, nitrogen usually has an oxidation number of -3.
Each of the hydrogen atoms in H2 has an oxidation number of 0.
-2
Negative (such as -2 in compounds like O2 or Cl-) or positive (such as +3 in compounds like NCl3), depending on the element and the compounds involved.
Usually, oxygen has an oxidation of -2 (that is unless in a compound with peroxides or halogens).
In the compound Al₂O₃, aluminum has an oxidation number of +3, and oxygen has an oxidation number of -2. This gives a total charge of zero for the compound, as it should be electrically neutral.
In K2MnF6, +1 for K, +4 for Mn and -1 for F In SbF5, +5 for Sb and -1 for F In KSbF6, +1 for K, +5 for Sb and -1 for F In MnF3, +3 for Mn and -1 for F In F2, 0 for F
An example is the ferric ion: Fe(III) or Fe3+.
The oxidation number of Al in Al2Br6 is +3. Each bromine atom has an oxidation number of -1, and since the compound is neutral, the sum of the oxidation numbers must equal zero. Hence, each Al atom must have an oxidation number of +3 to balance the -6 from the bromine atoms.