What is the exact method/formula used to calculate oxidation state #'s? & how does one know when to use the correct oxidation state #? For example: Carbon carries 4,2,-4; Cl= 1,5,7,-1; and, Mn=2,3,4,7.
Thanx.
You use the seven rules in your text.
Assigning of the oxidation numbers in a compound is arbritary, and based exclusively on these rules.
http://chemistry.about.com/od/generalchemistry/a/oxidationno.htm
The calculation of oxidation numbers is based on a set of rules that can be used to assign oxidation numbers to elements in a compound. Here are the general guidelines for determining the oxidation number:
1. The oxidation number of an uncombined element is always zero. For example, the oxidation number of carbon in its pure form (diamond or graphite) is always zero.
2. The oxidation number of a monatomic ion is equal to its charge. For example, the oxidation number of Cl- (chloride ion) is -1.
3. The sum of the oxidation numbers in a neutral compound is always zero. For example, in H2O, the oxidation number of hydrogen is +1 and the oxidation number of oxygen is -2, which balances out to zero.
4. In most compounds, oxygen has an oxidation number of -2. There are a few exceptions, such as peroxides (e.g., H2O2), where oxygen has an oxidation number of -1.
5. Hydrogen typically has an oxidation number of +1 when bonded to nonmetals and -1 when bonded to metals.
6. The sum of the oxidation numbers in a polyatomic ion must equal the charge of the ion. For example, in the sulfate ion (SO42-), the oxidation number of sulfur can be calculated by setting up the equation: oxidation number of sulfur + 4 × oxidation number of oxygen = -2 (charge of the sulfate ion).
7. Some elements have specific oxidation numbers in certain compounds. For example, alkali metals like sodium (Na) and potassium (K) always have an oxidation number of +1 in compounds, and alkaline earth metals like magnesium (Mg) always have an oxidation number of +2.
To determine the correct oxidation number for a specific element, you need to apply these rules to the compound in question. For example, for carbon, you mentioned that it can have oxidation numbers of +4, +2, and -4. The specific oxidation number for carbon depends on the compound it is in.
In the case of chlorine (Cl), you mentioned oxidation numbers of +1, +5, +7, and -1. Again, the specific oxidation number for chlorine depends on the compound it is in.
Similarly, for manganese (Mn), you mentioned oxidation numbers of +2, +3, +4, and +7. The specific oxidation number for manganese depends on the compound it is in.
It's important to note that the assignment of oxidation numbers is arbitrary and based solely on these rules. Different compounds with the same elements can have different oxidation numbers. Therefore, it's necessary to consider the specific compound and apply the rules to determine the correct oxidation number for each element.