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Ch.22 - The Main Group Elements
Chapter 22, Problem 22.126

Arrange the following oxides in order of increasing basic character: Al2O3, Cs2O, K2O, N2O5.

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Identify the type of oxides: Al2O3 is an amphoteric oxide, Cs2O and K2O are basic oxides, and N2O5 is an acidic oxide.
Understand the periodic trend: Basicity of oxides increases down a group and decreases across a period from left to right in the periodic table.
Recognize that acidic oxides are less basic than amphoteric oxides, which are less basic than basic oxides.
Arrange the oxides based on their basic character: N2O5 (acidic) < Al2O3 (amphoteric) < K2O (basic) < Cs2O (more basic).
Verify the order by considering the position of the elements in the periodic table: Cs is below K in Group 1, making Cs2O more basic than K2O.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Basicity of Oxides

Basicity refers to the ability of a substance to accept protons (H+) or donate electron pairs. In the context of metal oxides, basic character increases with the metallic nature of the element. Alkali metal oxides, such as K2O and Cs2O, are typically more basic than oxides of metalloids or nonmetals, like Al2O3 and N2O5.
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Metallic vs. Nonmetallic Oxides

Metallic oxides are generally basic, while nonmetallic oxides tend to be acidic or amphoteric. For example, Al2O3 is amphoteric, meaning it can act as both an acid and a base, while N2O5 is acidic. Understanding the nature of the elements involved helps in predicting the basicity of their oxides.
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Trends in Oxide Basicity

The basicity of oxides typically increases down a group in the periodic table due to the increasing metallic character of the elements. For instance, alkali metal oxides are more basic than alkaline earth metal oxides, and this trend helps in arranging the given oxides based on their basic character.
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