Intermediate Topic 655 of 1102 Inorganic Chemistry
Oxides
Oxides can be acidic, basic, amphoteric or neutral depending on the element.
In-depth explanation of Oxides
Oxides are compounds of oxygen with other elements, and their acid-base character is a useful way to classify them. Basic oxides, formed by metals such as CaO and Na2O, react with acids and dissolve to give alkaline solutions. Acidic oxides, formed by nonmetals such as SO3 and CO2, react with water to give acids. Amphoteric oxides, such as Al2O3 and ZnO, react with both acids and bases, while neutral oxides such as CO and N2O show neither behaviour. As the oxidation state of an element rises, its oxide generally becomes more acidic, so CrO is basic, Cr2O3 is amphoteric and CrO3 is acidic.
Going deeper: Oxides
Key ideas: Classify by behavior: acidic (CO2, SO3, P4O10, nonmetal oxides), basic (Na2O, CaO, metal oxides), amphoteric (Al2O3, ZnO, PbO, BeO), and neutral (CO, NO, N2O, H2O). Acidic character rises with oxidation state and across a period: Na2O basic, MgO basic, Al2O3 amphoteric, SiO2 weakly acidic, P4O10 acidic, SO3 strongly acidic. Mixed oxides such as Fe3O4 and Pb3O4 contain two oxidation states.
Common mistakes and connections: Students decide acidity from the presence of oxygen alone, or mistake H2O for acidic or basic. Amphoteric oxides react with both acid and base, not with water in general. Higher oxidation state of the same metal gives a more acidic oxide: CrO is basic, Cr2O3 amphoteric, CrO3 acidic. Links to periodic trends, acid-base theory and nomenclature.
Visualization of Oxides
Acidic oxides give acids and basic oxides give alkalis when dissolved in water; neutral and amphoteric oxides lie between. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Chromium(VI) oxide, CrO3, dissolves in water to give chromic acid, H2CrO4.
Frequently asked questions about Oxides
What is Oxides?
Oxides can be acidic, basic, amphoteric or neutral depending on the element.
Is Oxides a beginner, intermediate or advanced topic?
Oxides is a intermediate topic in Inorganic Chemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before Oxides?
Study these earlier topics in Inorganic Chemistry first: Fertilizers, Oxygen Family, Ozone.
What comes after Oxides?
The next topics in Inorganic Chemistry are Sulfur Allotropes and Sulfur Dioxide.
Can I practise Oxides with quizzes?
Yes. The interactive lesson includes a self-check question on Oxides, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Oxides fits in Inorganic Chemistry
Oxides is topic 40 of 113 in Inorganic Chemistry.