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Simple Oxides – Definition, Types, Examples

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  • Last Updated : 01 Feb, 2022

Oxides are binary chemicals generated when oxygen reacts with other elements. In nature, oxygen is extremely reactive. They create oxides when they react with metals and nonmetals. Based on their acid-base properties, oxides are classified as neutral, amphoteric, basic, or acidic.

  1. An acidic oxide is an oxide that produces acid when mixed with water.
  2. When water is added to a basic oxide, the result is a base.
  3. An amphoteric solution is formed when a material reacts chemically, either as a basic or an acid.
  4. A neutral oxide is one that has neither an acidic nor a basic property.

Metal oxides have an oxidation number of -2 and are typically made up of an oxygen anion. The Earth’s crust is largely composed of solid oxides. Oxide coatings can also form on pure elements; for example, a foil made of aluminum is coated by a thin skin of Al2O3, which protects the rest of the foil from corrosion.

Simple Oxides

Oxides are further classified into two types: simple and many. Simple oxides are composed of a single metal coupled with oxygen in one of several metal-oxygen ratios: XO, X2O, X2O3, and so on. Ice, H2O, is a simple X2O oxide that contains hydrogen as the cation. Multiple oxides with the formula XY2O4 have two non-equivalent metal sites (X and Y).

When two simple oxides are combined, we get a mixed oxide. For example, lead dioxide (PbO2) and lead monoxide (PbO) combine to generate the mixed oxide Red lead (Pb3O4). In another case, ferric oxide (Fe2O3) and ferrous oxide (FeO) combine to generate the mixed oxide Ferro-ferric oxide (Fe3O4). Let’s see about the classification of simple oxides,

  • Basic oxide

Metals react with oxygen to form basic oxygen compounds. Ionic compounds are the most common type of these chemicals. When groups 1, 2, and lanthanides react with dioxygen, they generate basic oxygen compounds. A considerable quantity of energy is released during the synthesis of these molecules. Except for a few exceptions, these chemicals readily react with water. Examples are M2O3, MO2, and ThO2.

Na2O + H2O → 2NaOH

  • Acidic oxide

Nonmetals react with oxygen to generate acidic oxide compounds bound together by covalent bonds. These chemicals are also known as acid anhydrides. Except for substances like B2O3 and SiO2, which have high melting points and form large molecules, acid anhydrides typically have moderate melting and boiling points. NO, CO2 is two examples.

SO3 + H2O → H2SO4

  • Amphoteric oxide

Amphoteric oxides are oxygen compounds that have both acidic and basic properties. When these oxides combine with acid, they undergo a neutralization process, resulting in the formation of water and salt. This demonstrates the fundamental feature of the compounds. Similarly, it combines with alkali to generate salt and water, displaying acidic properties. Aluminum oxide is an example.

Acidic characteristics

Al2O3 + 6HCl → 2Al3+ + 6Cl + 3H2O

Basic characteristics

Al2O3 +2OH + 3H2O → 2[Al(OH)4]

  • Neutral Oxides

Some chemicals react with oxygen to generate oxides that are neither acidic nor basic. Such molecules are referred to as oxygen neutral compounds. NO, CO is two examples.

Other types of oxides

Other types of oxides include polymeric oxides, molecular oxides, and compound oxides. Let’s understand about these types of oxides in detail,

  • Polymeric oxides

Oxygen is coupled with multiple metallic atoms in oxides with a crystalline structure, resulting in a polymeric bonding and oxide structure. Titanium oxide crystals, for example, have a rutile structure in which each titanium is surrounded by six oxygen atoms, and each oxygen is triangularly connected to three titanium. Other unit cells are involved in the bonding atom. As with polymer synthesis from a monomer, this requires the participation of numerous unit cells. As a result, these oxides are classified as polymeric oxides.

  • Molecular oxides

Molecular oxides are binary oxides that exist as individual molecules. Oxides with simple atomic ratios are typically molecular. Molecular oxides include carbon/nitrogen oxides and halogen oxides. At higher temperatures, some polymeric and crystalline oxides, such as phosphorus pentoxide, selenium dioxide, and osmium tetroxide, depolymerize to molecular oxides.

  • Compound oxides 

This is a compound composed of one or more binary oxides. Fe3O4 is a compound composed of FeO and Fe2O3.

  • Surface and Bulk Oxides

The strong reactive metal completely reacts to generate oxides across the entire volume. Less reactive metals such as aluminum, noble metals such as silver, and gold only react with oxides near the surface. The surface oxide prevents oxygen from entering the interior and reacting with the atoms in the bulk.

Sample Problems

Question 1: What is an oxide?

Answer:

Oxides are binary chemicals created when oxygen reacts with other elements.

Question 2: What are neutral oxides?

Answer:

When certain substances react with oxygen, they generate oxides that are neither acidic nor basic. The term “neutral oxygen compounds” refers to such substances. Example: NO, CO.

Question 3: Write a short note on basic oxides.

Answer:

Basic oxygen compounds are formed when metals react with oxygen. The majority of these chemicals are ionic in nature. When group 1, 2, and lanthanides react with dioxygen, they produce basic oxygen compounds. A lot of energy is released during the synthesis of these molecules. Except for a few exceptions, these chemicals readily react with water.

Question 4: What is an amphoteric oxide?

Answer:

Amphoteric oxides are oxygen-based molecules that have both acidic and basic properties. When these oxides combine with acid, a neutralisation reaction occurs, resulting in the formation of water and salt.

Question 5: What are surface and bulk oxides?

Answer:

Oxygen-based compounds with acidic and basic characteristics are known as amphoteric oxides. A neutralisation process happens when these oxides react with acid, resulting in the creation of water and salt.

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