Problem 79 - A Complete Resource Book in Chemistry for JEE Main

Question

An element (A) occurs in a short period having the configuration \(\mathrm{ns}^{2} \mathrm{np}^{1}\). The formula and nature of its oxide is (a) \(\mathrm{AO}_{3}\), acidic (b) \(\mathrm{A}_{2} \mathrm{O}_{3}\), amphoteric (c) \(\mathrm{AO}_{3}\), basic (d) \(\mathrm{A}_{2} \mathrm{O}_{3}\), basic

Step-by-Step Solution

Answer

(b) \( \text{A}_2\text{O}_3 \), amphoteric.

Step 1: Determine the Group of the Element

The element is in a short period with the electron configuration \( ext{ns}^2 ext{np}^1 \). This configuration indicates that the element is in Group 13 of the periodic table, typically referred to as the Boron group.

Step 2: Consider Possible Oxidation States

Elements in Group 13 typically have a common oxidation state of +3. We will use this information to determine the oxide formula.

Step 3: Determine the Oxide Formula

Since the typical oxidation state of the element is +3, its oxide can be identified as \( ext{A}_2 ext{O}_3 \). This is derived by balancing the charges between the +3 oxidation state of the element (A) and the -2 charge of oxygen.

Step 4: Identify the Nature of the Oxide

The nature of the oxide formed by Group 13 elements in this configuration is often amphoteric. Amphoteric oxides can react with both acids and bases. One common example is aluminum oxide \( ext{Al}_2 ext{O}_3 \).

Key Concepts

Electron Configuration

The electron configuration of an element is essential to understanding its chemical behavior. For Group 13 elements, characterized by the electron configuration \( \mathrm{ns}^{2} \mathrm{np}^{1} \), this implies that there are a total of three electrons in the outermost shell. The "n" represents the principal quantum number, which signifies the shell in which the electrons are located. This configuration indicates that Group 13 elements are in the p-block of the periodic table.
These elements include Boron (B), Aluminum (Al), Gallium (Ga), Indium (In), and Thallium (Tl). Their unique electron configuration contributes to their chemical properties, such as often having an oxidation state of +3 due to the need to achieve a stable octet by losing these three outer electrons.

Oxidation States

Oxidation states, also known as oxidation numbers, indicate the degree of oxidation of an atom in a compound. Group 13 elements commonly exhibit a +3 oxidation state. This arises because they have three valence electrons that they tend to lose, which results in a stable electronic configuration similar to that of noble gases.
While +3 is the most common oxidation state, some elements in Group 13 may also show other oxidation states, such as +1, particularly in heavier elements like Gallium and Thallium. The variance in oxidation states can influence the type of compounds the elements form, as well as their reactivity and stability.

Oxide Formulas

The oxide formula for Group 13 elements is often derived by considering the oxidation state. With the typical oxidation state being +3, the general oxide formula corresponds to \( \mathrm{A}_{2} \mathrm{O}_{3} \). This occurs because the +3 oxidation state of each element balances with the -2 charge of oxygen to maintain electrical neutrality.
For example, Aluminum, a Group 13 element, forms Aluminum Oxide \( \mathrm{Al}_{2} \mathrm{O}_{3} \), where two Al atoms (with +3 charge each) balance three O atoms (with -2 charge each). This is a common type of oxide formed by Group 13 elements, signaling their role in various chemical reactions.

Amphoteric Oxides

Amphoteric oxides are unique as they have the ability to react with both acids and bases. Many oxides of Group 13 elements, such as \( \mathrm{Al}_{2} \mathrm{O}_{3} \) or Aluminum Oxide, exhibit amphoteric behavior. This is due to the oxides' ability to donate or accept protons, depending on the surrounding chemical environment.
This amphoteric nature is largely attributed to the intermediate position of Group 13 elements within the periodic table, as they exhibit characteristics of both metals and nonmetals. For example, \( \mathrm{Al}_{2} \mathrm{O}_{3} \) will form aluminum hydroxide in the presence of bases, and aluminum salts when dissolved in acids. This dual reactivity makes amphoteric oxides fascinating and useful in various industrial and chemical processes.