Problem 11 - Chemistry and Chemical Reactivity

Question

Place the following oxides in order of increasing basicity: \(\mathrm{CO}_{2}, \mathrm{SiO}_{2}, \mathrm{SnO}_{2}.\)

Step-by-Step Solution

Answer

The order of increasing basicity is: \(\mathrm{CO}_{2} < \mathrm{SiO}_{2} < \mathrm{SnO}_{2}\).

Step 1: Understanding Basicity in Oxides

The basicity of an oxide is determined by the metallic character of the element it's composed of. More metallic elements form more basic oxides, while less metallic (more nonmetallic) elements form acidic oxides.

Step 2: Identify Element Types

List the elements in each oxide and classify each element as metal or nonmetal. In our list, we have: \(\mathrm{C}_{(Nonmetal)}\), \(\mathrm{Si}_{(Metalloid)}\), and \(\mathrm{Sn}_{(Metal)}\).

Step 3: Order by Metallic Character

Order the elements by increasing metallic character: \(\mathrm{C}<\mathrm{Si}<\mathrm{Sn}\). This order reflects the increasing basicity of their respective oxides.

Step 4: Final Order of Oxides

Thus, the order of the oxides from least to most basic is as follows: \(\mathrm{CO}_{2} < \mathrm{SiO}_{2} < \mathrm{SnO}_{2}\). \(\mathrm{CO}_{2}\) is acidic, \(\mathrm{SiO}_{2}\) is weakly acidic with some neutrality, and \(\mathrm{SnO}_{2}\) is slightly basic.

Key Concepts

Metallic Character

The metallic character of an element refers to how readily it loses electrons to form positive ions, also known as cations. This property is often associated with elements that are positioned on the left side of the periodic table.
As we move from left to right across a period, the metallic character decreases; this is due to increased nuclear charge which holds the electrons more tightly.
For instance, elements like sodium (\(\mathrm{Na}\)) have a high metallic character and form basic or alkaline oxides.

• Metals have high metallic character.
• Metalloids have intermediate metallic character.
• Non-metals have low metallic character.

Understanding where an element stands in terms of metallic character helps predict the reactivity and type of oxides it forms.
Metals typically form basic oxides, while non-metals form acidic oxides. Metalloids like silicon (\(\mathrm{Si}\)) can form oxides that have both acidic and basic properties, making them amphoteric.

Acidic and Basic Oxides

Oxides are compounds formed by the reaction of oxygen with an element. They can be classified based on their behavior as acidic or basic, depending on the nature of the element they are combined with.
Acidic oxides usually result from the combination of oxygen with nonmetals. For example, carbon dioxide (\(\mathrm{CO}_2\)) is an acidic oxide because it reacts with water to form carbonic acid.

• Acidic oxides: react with bases to form salt and water.
• Basic oxides: react with acids to form salt and water.

Basic oxides generally come from metals. They can dissolve in water to produce hydroxides, which are basic. An example is sodium oxide (\(\mathrm{Na}_2\mathrm{O}\)), which dissolves in water to form sodium hydroxide (\(\mathrm{NaOH}\)).
Surprisingly, there are oxides like silicon dioxide (\(\mathrm{SiO}_2\)) that can exhibit behaviors of both acidic and basic oxides, depending on the reacting conditions, making them amphoteric.

Chemical Properties of Elements

The chemical properties of elements influence how they interact with other substances, including the formation of oxides.

• Nonmetals form oxides that tend to possess acidic characteristics, like \(\mathrm{CO}_2\).
• Metalloids form oxides that can be amphoteric, such as \(\mathrm{SiO}_2\).
• Metals typically create basic oxides, such as \(\mathrm{SnO}_2\).

These properties are determined by the elements' ability to either accept or donate electrons during chemical reactions.
This electron exchange either strengthens or stabilizes the oxides they form.
The periodic table serves as a useful tool for predicting these chemical properties because it organises elements by their reactivity and electronic configurations.Understanding these properties helps not only in ordering the basicity of oxides but also in predicting the reactions of elements during chemical processes.