Problem 122 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following: List I List II 1\. most electronegative (i) \(\mathrm{I}_{2}\) 2\. most electron affinity (ii) At 3\. liquid halogen (iii) \(\mathrm{F}_{2}\) 4\. radio active halogen (iv) \(\mathrm{Cl}_{2}\) (v) \(\mathrm{Br}_{2}\) The correct matching is: \(\begin{array}{llll}1 & 2 & 3 & 4\end{array}\) (a) (iii) (iv) (v) (ii) (b) \(\begin{array}{ll}\text { (iii) (iv) } & \text { (v) }\end{array}\) (i) (c) (ii) (i) (iii) (iv) (d) \(\begin{array}{llll}\text { (iii) (i) } & \text { (ii) } & \text { (iv) }\end{array}\)

Step-by-Step Solution

Answer

(a) (iii) (iv) (v) (ii)

Step 1: Identify the Most Electronegative Element

The most electronegative element is fluorine, denoted by \( \mathrm{F}_{2} \), among the elements listed in List I. Thus, match 1 with (iii).

Step 2: Identify the Element with the Most Electron Affinity

Chlorine has the highest electron affinity. Therefore, match 2 with (iv), \( \mathrm{Cl}_{2} \).

Step 3: Determine the Liquid Halogen

At room temperature, bromine is the only halogen that is in a liquid state. Hence, match 3 with (v), \( \mathrm{Br}_{2} \).

Step 4: Detect the Radioactive Halogen

Astatine, represented as At, is a radioactive halogen. Thus, match 4 with (ii) At.

Key Concepts

Electronegativity

Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond. Among all elements, fluorine is known as the most electronegative. This strong ability to attract electrons is due to fluorine's small size and high effective nuclear charge, which tightly holds onto its electrons while drawing in additional ones.
This electronegative property makes fluorine a highly reactive element, particularly with metals, as it forms ionic compounds by taking electrons from them. In the original exercise, the most electronegative option given was fluorine (8F_{2}). Its unmatched ability to attract electrons is crucial in many chemical reactions and processes.

Electron Affinity

Electron affinity refers to the ability of an atom to accept an electron, often resulting in the release of energy. Halogens tend to have high electron affinities, meaning they easily gain electrons to form negative ions. Among halogens, chlorine (8Cl_{2}) has the highest electron affinity.
This means that when an electron is added to a chlorine atom, a significant amount of energy is released as the atom achieves greater stability. Electron affinity is an important concept in predicting how atoms will interact in chemical reactions, with high electron affinity often leading to negative ion formation. In the exercise, we matched chlorine as the halogen with the most electron affinity.

State of Matter of Halogens

Halogens exist in different states of matter at room temperature, distinguishing them from one another. Fluorine and chlorine are gaseous, while iodine and astatine are solid under standard conditions. Bromine (8Br_{2}), unique among these, exists as a liquid at room temperature.
This distinct property is due to bromine's intermolecular forces, which are stronger than those in fluorine and chlorine but weaker than those in iodine and astatine. These forces keep bromine in a liquid state, serving a critical role in understanding halogen chemistry and practical applications, such as in industrial chemistry.

Radioactive Elements

Radioactive elements are those that exhibit radioactivity, meaning they emit radiation as they decay. Among halogens, astatine (At) is the well-known radioactive element. It is rare and has a very short half-life, meaning it decays quickly into other elements, emitting alpha particles as it does so.
In the exercise, astatine was identified as the radioactive element due to its decay properties. Its radioactivity has potential uses in medical therapies, such as targeted cancer treatments, where it can specifically target diseased cells while sparing the surrounding healthy tissue. However, handling radioactive elements requires careful safety and ethical considerations.