Oxides change from basic on the left of a period through amphoteric to acidic on the right.
Practise Atomic Structure & Periodicity All Atomic Structure & Periodicity topics
Across period 3 the oxides change from basic through amphoteric to acidic. Sodium oxide is strongly basic and dissolves to give hydroxide, aluminium oxide is amphoteric and reacts with both acids and bases, and oxides such as sulfur trioxide and dichlorine heptoxide are acidic. This trend reflects decreasing metallic and increasing covalent character of the bonding as the nonmetal side is approached. The oxidation state of the element rises across the period, which also increases the acidity of its oxide. Oxide acidity helps explain the behaviour of many environmental pollutants.
Key ideas: Across period 3 oxides change from basic (Na2O, MgO) to amphoteric (Al2O3) to acidic (SiO2, P4O10, SO3, Cl2O7), with bonding changing from ionic to covalent. Basic oxides plus water give hydroxides (Na2O + H2O gives 2 NaOH), acidic oxides give acids (SO3 + H2O gives H2SO4). Within a group, basicity increases down.
Common mistakes and connections: Students think all oxides are basic or that CO and NO are acidic (they are neutral oxides). Amphoteric Al2O3 dissolves in both acid and base. The oxide trend reflects the electronegativity difference with oxygen, and is applied to acid rain (SO2, NOx) and to the periodicity of oxoacid strength.
Period 3 oxides change from strongly basic Na2O to amphoteric Al2O3 to strongly acidic SO3, as shown by the pH of their solutions. The interactive lesson shows this as a live animation or chart.
Na2O reacts with water to give sodium hydroxide, whereas SO3 reacts with water to give sulfuric acid.
Oxides change from basic on the left of a period through amphoteric to acidic on the right.
Periodic Trends in Oxides is a intermediate topic in Atomic Structure & Periodicity. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Atomic Structure & Periodicity first: Inert Pair Effect, Lanthanide Contraction, Periodic Trends in Oxidation State.
The next topics in Atomic Structure & Periodicity are Hydrogen Position and Quark Structure of Nucleons.
Yes. The interactive lesson includes a self-check question on Periodic Trends in Oxides, and the Atomic Structure & Periodicity quiz draws on every topic in this area.
Periodic Trends in Oxides is topic 98 of 115 in Atomic Structure & Periodicity.