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The oxidation number represents the charge on an atom; it could be positive, negative, or neutral. It is essential to assign an oxidation number to an atom in an equation so that you can come across the oxidation or reduction of an element. In this article, you will be reading rules to assign oxidation numbers as well as You will see the difference in the oxidation numbers at different elements in an equation.
What is the oxidation number?
Different elements either gain electrons or lose electrons during a chemical reaction to form a bond with another element. When an atom loses electrons, it gains a positive charge. It gains a negative charge; sometimes, the elements remain neutral without gaining or losing any electron. A number is assigned to each element indicating their charge while losing or gaining the electrons; this numerical representation is called oxidation number.
For example, Ca2+, calcium lost 2 Electrons and hence gained 2 positive charges; therefore, its oxidation number is + 2. O2-, oxygen gains 2 electrons and has 2 negative charges; therefore, its operation number is -2.
How does the oxidation number represent oxidation or reduction?
When an atom undergoes oxidation, it loses electrons, hence gaining a positive charge which means when an atom’s oxidation number is increased, it is being oxidised. Whereas when an atom undergoes reduction, it gains electrons and a negative charge is acquired by it, which means the atom is being reduced with the decrease in the oxidation number.
How to calculate oxidation number?
The answer to the question, how to calculate oxidation number is the one you can’t just give in one word. It is a very elaborate answer. Let’s see the rules to calculate the oxidation number of an element.
Rule 1. When an element is a pure form, its oxidation number is considered as zero.
An element is considered in its pure form when it is stable without combining with any other element. However, it can combine with itself.
Rule 2. The oxidation number of an ion is precisely equal to the charge it holds.
When an element is in its ionic form, it contains a charge which could be positive or negative, so simply the oxidation number is precisely what the charge on the ion is.
Rule 3. The oxidation number of metals is the same as their groups.
The oxidation number in metal from group one is plus one and the metals from group 2 have oxidation number plus 2. According to the modern periodic table the metals are Placed in Group one in 2 Groups; metals possess an oxidation number precisely equal to the number of groups they are in.
Rule 4. The case of a hydrogen atom is a bit different; hydrogen poses 2 different oxidation numbers, plus one and -1.
Rule5. Oxygen poses a variety of oxidation numbers. The oxidation number of oxygen varies between These 3 -2, 2 and -1.
Generally, oxygen has oxidation number -2, but in exceptional cases like, oxygen in Peroxides poses oxidation number -1 and shows oxidation number + 2 in difluorides.
Rule 6. The oxidation number of fluorine is -1 in every case.
Rule 7. For other halogens like chlorine bromine and iodine doc station number in maximum cases is -1 very well they are combined with oxygen and fluorine.
In compounds like sodium chloride, chlorine shows oxygen state -1. In contrast, Cl in compounds like perchloride it also shows the Occidente state as plus 7 and in compounds like Hypochlorous Acids, chlorine shows oxygen state equals To 1.
Rule 8. When we add the oxidation number of all elements in a naturally occurring compound, the sum is always equal to zero.
In all the naturally occurring compounds like HCl or aa NaOH, the oxidation number of each element is equal to zero.
Let us see some examples to check our understanding of oxidation numbers.
Example 1. Calculate the oxidation number of underlined elements.
- NaCl
- CaF2
- SF6
- PCl5
Solution.
Let us consider NaCl as a naturally occurring compound; hence NaCl has the overall oxidation state as zero. Now we clearly know that Na has an oxidation number equal to one as it is a metal from Group One.
Therefore now,
1+x=0
X= -1
The oxidation number of Cl in NaCl is -1.
Let us consider CF2 as a naturally occurring compound; hence CF 2 have an overall oxidation state that is equal to zero now we clearly know that fluorine has oxidation state is equals to – 2
Therefore now
x + (-1)*2= 0
x=0- (-2)
x=2
Oxidation number of ca in CF2 is + 2.
SF6 is a naturally occurring compound hence the overall oxidation state is equals to zero now we already know that oxidation state of fluorine is -1
Therefore now
x+(-1)*6=0
x = 6
Oxidation number of sulphur in SF6 is +6.
PCL 5 is again a naturally occurring compound heads the overall oxidation state is equal to zero now we already know the oxidation number of chlorine is equals to -1
Therefore now
x+(-1)*5=0
x=5
Oxidation number of phosphorus in PCl5 is + 5.
Conclusion
The oxidation number of an element in a compound or in general is calculated to see or check whether it is being oxidised or reduced. In a written chemical equation If the oxidation number increases the element is oxidised otherwise it is reduced. We have discussed different rules and regulations of determining oxidation number for an element in its compound or natural or pure form. We hope this article helped you.
