IUPAC Nomenclature of Inorganic Compounds | Chemistry for JAMB PDF Download

Introduction

Understanding the IUPAC nomenclature of inorganic compounds and the concept of oxidation numbers is crucial for students studying chemistry. In this article, we will delve into the intricacies of these topics, exploring the relationship between oxidation numbers and valency, as well as examining the rules and examples of assigning oxidation numbers to different elements. By the end, you will have a firm grasp on these fundamental concepts, enabling you to navigate the world of inorganic chemistry with confidence.

The Relationship between Oxidation Numbers and Valency

The oxidation number, also known as the oxidation state, is a measure of the charge carried by an element in a compound. In other words, it represents the number of electrons gained or lost by an atom of an element when forming a compound.

Assigning Oxidation Numbers: Rules and Examples

To assign oxidation numbers to different elements in a compound, several rules need to be followed. Here are the key rules:

• The valency of a metal carries a positive charge, while the valency of a non-metal carries a negative charge.
• The total oxidation state of any compound is always zero, obtained by summing the oxidation numbers of all the elements in the compound.
• Some elements exhibit variable oxidation states, such as copper, lead, nitrogen, and iron.

Let's look at an example to illustrate the process of assigning oxidation numbers:
Compound: Zinc chloride (ZnCl₂)

• The oxidation number of Zn (zinc) = +2
• The oxidation number of Cl (chlorine) = -1
• Calculation: +2 + (2 x -1) = +2 - 2 = 0

Thus, the oxidation numbers of Zn and Cl in ZnCl₂ are +2 and -1, respectively.

Examples of Compounds and their IUPAC Names

Now, let's explore some examples of compounds and their corresponding IUPAC names based on their oxidation numbers:

Example 1: Nitrogen compounds:

• N₂O - Dinitrogen (I) oxide, oxidation state of nitrogen = +1
• NO - Nitrogen (II) oxide, oxidation state of nitrogen = +2
• NH₃ - Ammonia, oxidation state of nitrogen = -3
• NO₂ - Nitrogen (IV) oxide, oxidation state of nitrogen = +4
• NO₃^- - Trioxonitrate (V), oxidation state of nitrogen = +5

Example 2: Manganese compound:
Compound: Potassium tetraoxomanganate (VII) (KMnO₄)
Oxidation state of manganese (Mn) = +7

Example 3: Chromium compound:
Compound: Potassium heptaoxodichromate (VI) (K₂Cr₂O₇)
Oxidation state of chromium (Cr) = +6

Section 4: Exercises to Test Your Knowledge
To reinforce your understanding, here are a few exercises to tackle:

Exercise 1: 3NH₃ represents:
(a) three moles of ammonium
(b) three moles of ammonia
(c) six moles of ammonia
(d) six moles of ammonium

Exercise 2: What is the oxidation number of sulfur in H₂SO₄?
(a) +2
(b) +4
(c) +6
(d) +7

Exercise 3: Find the oxidation number of the manganese atom in KMnO₄.
(a) +7
(b) -7
(c) +6
(d) -6

Exercise 4: _________ is the charge on the valency of an element.
(a) reduction number
(b) mole number
(c) oxidation number
(d) isotopy

Exercise 5: What is the IUPAC name of the compound Fe₂O₃?
(a) iron (II) oxide
(b) iron monoxide
(c) iron (IV) oxide
(d) iron (III) oxide

Conclusion

Mastering the IUPAC nomenclature of inorganic compounds and the concept of oxidation numbers is essential for any chemistry student. By understanding the relationship between oxidation numbers and valency and following the rules for assigning oxidation numbers, you can confidently navigate through various compounds and name them accurately. Remember to practice through exercises to reinforce your knowledge and keep exploring the fascinating world of chemistry.