Calculation of Oxidation Number An oxidation number is a numerical value assigned to an atom or ion that indicates its charge. It is calculated by subtracti...
Calculation of Oxidation Number
An oxidation number is a numerical value assigned to an atom or ion that indicates its charge. It is calculated by subtracting the number of electrons lost or gained by the atom from the number of electrons gained or lost by any ions the atom has gained or lost.
For instance, if an atom loses an electron, its oxidation number will increase, while if an atom gains an electron, its oxidation number will decrease. The oxidation number is typically indicated by a Roman numeral or a chemical symbol.
Rules for Calculating Oxidation Number
Atoms in the same group have the same oxidation numbers. This is because they have the same number of valence electrons, which are the electrons that participate in bonding.
Atoms in a compound have the oxidation numbers of the elements in the compound. This is because the oxidation numbers of the elements add up to the total oxidation number of the compound.
The oxidation number of an ion is equal to the charge of the ion. This is because the oxidation number tells us how many electrons an atom has lost or gained.
Examples
In NaCl (sodium chloride), the oxidation number of sodium is +1, while the oxidation number of chlorine is -1.
In H2O (water), the oxidation number of hydrogen is +1, while the oxidation number of oxygen is -2.
In CaCO3 (calcium carbonate), the oxidation number of calcium is +2, while the oxidation number of carbon is -4, and the oxidation number of oxygen is -2.
By understanding the concept of oxidation numbers and following the rules for calculating them, students can accurately predict the oxidation state of atoms and ions in chemical compounds