Introduction

Relevance of the Theme

Understanding Inorganic Functions, a fundamental pillar in Chemistry, is crucial for the comprehension of chemical reactions and for the study of various fields, such as Biochemistry, Materials Engineering, and Geology. Oxides, in particular, have a wide range of practical applications, from the formation of acid rains to the manufacturing of glasses and ceramics.

Contextualization

In the vast universe of Inorganic Functions, Oxides are a special category that deserves special attention. Their structure, properties, and reactivity are interconnected and dynamic. They act as bases or acids depending on the medium in which they are found, showing the versatility of Inorganic Chemistry.

Oxides are the first group of compounds that we study in depth in the 1st year of High School, after the basic study of atoms and molecules. They serve as the basis for the study of chemical reactions and the formation of other Inorganic Functions. Their analysis provides the construction of a solid theoretical foundation that will support the understanding of more advanced concepts in the Chemistry discipline, both at the school level and in academic or professional settings.

Theoretical Development

Components

• Oxides: are binary compounds formed by the combination of a chemical element (commonly a metal) with oxygen.

  • They can be classified into Metallic Oxides, when the metal has only one valence, and Non-Metallic Oxides (or Anhydrides), when the metal has more than one valence.

  • The nomenclature of metallic oxides follows the pattern "oxide of (metal name)" and non-metallic oxides follows the pattern "oxide of (numerical prefix) (non-metal name)".

• Properties of Oxides:

  • The main properties of Oxides are physical and chemical. Among the physical properties, we highlight the physical state (they can be solid, liquid, or gaseous), the melting and boiling temperature, density, and solubility.

  • Chemically, Oxides are reactive and can undergo various reactions, such as reacting with water to form acids (Non-Metallic Oxides) or bases (Metallic Oxides).

  • The properties of Oxides vary according to the element that composes it and the valence of that element.

Key Terms

• Reactivity: The ability of a substance to undergo chemical changes, resulting in the formation of new substances.

• Valence: The capacity that an atom has to combine with other atoms, forming chemical bonds. Indicates the number of electrons that an atom can gain, lose, or share.

• Nomenclature: System of rules used to name chemical compounds. In the case of Oxides, the nomenclature indicates whether the Oxide is metallic or non-metallic, in addition to providing information about the valence of the element.

Examples and Cases

• Examples of Metallic Oxides: Sodium Oxide (Na2O), Aluminum Oxide (Al2O3), and Calcium Oxide (CaO).

  • They are characterized by being solids at room temperature, having a high melting temperature, being soluble in water, forming basic solutions, and reacting with acids to form salt and water.

• Examples of Non-Metallic Oxides: Carbon Dioxide (CO2), Nitrogen Monoxide (NO), and Chlorine Oxide (Cl2O7).

  • They are generally gases or liquids, have low or no solubility in water, and can react with water to form acids, with metallic oxides to form salts, and with metals to form oxides and salts.

• Reactivity of Carbon Dioxide (CO2): CO2 is not considered an acidic oxide, but in the presence of water, it reacts to form carbonic acid (H2CO3), a reaction that is fundamental in balancing the pH of blood in mammals (including humans).

Detailed Summary

Relevant Points

• Oxides are binary compounds formed by the combination of a chemical element (usually a metal) with oxygen. Their nomenclature depends on whether they are metallic (metal name + oxide) or non-metallic (numerical prefix + non-metal name + oxide).
• The classification into Metallic Oxides and Non-Metallic Oxides depends on whether the element that combines with oxygen has only one valence or more than one.
• The properties of Oxides are physical (physical state, melting and boiling temperature, density, and solubility) and chemical (reactions with water to form acids or bases). These properties vary with the element and the valence of the element in the Oxide.
• Valence, a fundamental concept, indicates the ability of an atom to combine with other atoms. The valence of a metal is expressed by the Roman numeral after the name in the nomenclature of Metallic Oxide.
• The reactivity of an Oxide can be evidenced in reactions with water (formation of acids or bases), with metallic oxides (formation of salts), and with metals (formation of oxides and salts).

Conclusions

• Oxides, although apparently simple as they are formed by only two elements, represent a wealth of properties and chemical behaviors.
• The versatility of Oxides, which can act as acids or bases, serves as an illustration of the complexity and interconnection of chemical concepts.
• The nomenclature of Oxides provides valuable information about their behavior, including the valence of the element and, consequently, its reactivity.

Suggested Exercises

1. Classify the following compounds as Metallic Oxides or Non-Metallic Oxides, and give their nomenclature: Iron(III) Oxide, Calcium Oxide, Nitrogen Dioxide.

2. In the chemical reaction of Calcium Oxide with water, what is the result? Explain.

3. What is the expected reactivity of Phosphorus(III) Oxide in contact with water? Explain the reasoning.