Oxides
Oxides are binary compounds of oxygen with another element. Their formulas, names, preparation, and reactions reveal useful patterns connecting metals, nonmetals, acids, and bases.
Learning goals
- Recognize and name common oxides.
- Distinguish basic, acidic, and amphoteric behavior at an introductory level.
- Describe common preparation routes.
- Predict simple reactions from oxide class.
Recognition and naming
An oxide contains exactly two different elements, one of which is oxygen. In most school examples oxygen has oxidation state −2. Name the other element followed by “oxide”; when the element has several oxidation states, show its state with a Roman numeral: FeO is iron(II) oxide, while Fe2O3 is iron(III) oxide.
Basic oxides
Many metal oxides are basic. A basic oxide can react with an acid to form salt and water: $CuO+2HCl\rightarrow CuCl_2+H_2O$. Some active-metal oxides react with water: $CaO+H_2O\rightarrow Ca(OH)_2$.
Acidic oxides
Many nonmetal oxides are acidic. They can react with bases to form salt and water: $CO_2+2NaOH\rightarrow Na_2CO_3+H_2O$. Some react with water to form acids: $SO_3+H_2O\rightarrow H_2SO_4$.
Amphoteric oxides
Amphoteric oxides, such as Al2O3 and ZnO, can react with both acids and strong bases. At this grade, the key idea is “behavior in both directions”; detailed products can be studied later.