Problem 141 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following pairs is/are correctly matched here: (a) The strongest oxidizing agent - Iodine (b) The most reactive halogen - Fluorine (c) A halogen which is liquid at room temperature-Bromine (d) The most electronegative element-Fluorine

Step-by-Step Solution

Answer

Pairs (b), (c), and (d) are correctly matched.

Step 1: Identifying an Oxidizing Agent

An oxidizing agent is a substance that has a high tendency to gain electrons. Among halogens, fluorine is the strongest oxidizing agent, as it has the highest tendency to gain electrons, not iodine. Therefore, statement (a) is not correctly matched.

Step 2: Reactivity of Halogens

Among halogens, fluorine is the most reactive element due to its high electronegativity and small atomic size, which allows it to attract electrons more effectively than other halogens. Thus, statement (b) is correctly matched.

Step 3: State of Halogen at Room Temperature

At room temperature, bromine is indeed a liquid, distinguished by its dark red color. This makes statement (c) correctly matched.

Step 4: Electronegativity Comparison

Electronegativity is the tendency of an atom to attract a pair of electrons. Fluorine is known as the most electronegative element on the periodic table. Therefore, statement (d) is correctly matched.

Key Concepts

Halogen Reactivity

Halogens are a group of elements found in Group 17 of the periodic table. They include fluorine, chlorine, bromine, iodine, and astatine. These elements are highly reactive, which means they readily react with other substances. The reactivity of halogens decreases as you move down the group from fluorine to iodine. This trend is because the atoms increase in size down the group and the outer electrons are further from the nucleus, making it harder for the halogen to attract and gain an electron.
Fluorine is the most reactive of the halogens due to its small atomic size and high electronegativity. It can attract electrons more effectively than any other halogen, leading to vigorous reactions with most elements. Understanding the reactivity of halogens is crucial for predicting their behavior in chemical reactions.

Iodine Oxidizing Agent

An oxidizing agent is a substance that can accept electrons from another substance. Among the halogens, fluorine is the strongest oxidizing agent, not iodine. This is because fluorine has a greater ability to attract and gain electrons due to its high electronegativity and small atomic radius.
Iodine, on the other hand, is a weaker oxidizing agent compared to its fellow halogens like chlorine and bromine. It is less effective at gaining electrons because it is larger, and its outer electrons are further from the nucleus. Thus, while iodine is still an oxidizing agent, it is not the strongest among the halogen group.

Fluorine Electronegativity

Electronegativity is the measure of an atom's ability to attract and hold onto electrons within a chemical bond. Fluorine holds the title for the most electronegative element on the periodic table. This means it can pull electrons towards itself more effectively than any other element.
Fluorine's high electronegativity is due to its small atomic size, which allows the electrons to be more strongly attracted to its nucleus. This property makes fluorine extremely reactive, as it readily forms bonds with other elements to achieve a stable electronic configuration. Fluorine's electronegativity is a key factor in its role as a strong oxidizing agent.

Bromine State at Room Temperature

Bromine is unique among the halogens because it is the only one that is in a liquid state at room temperature. It has a dark red color and emits a pungent odor. The reason bromine is a liquid under standard conditions lies in the strength of the intermolecular forces between its molecules.
This intermediate state of bromine is due to its molecular structure which allows for liquid formation. Bromine's state at room temperature is a key characteristic that distinguishes it from other halogens like chlorine, which is a gas, and iodine, which is a solid.