Problem 8 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

(b) \(\mathrm{IC} 1\) (c) \(\mathrm{Cl}_{2}\) (d) \(\mathrm{Br}_{2}\)Which among the following is the most reactive? [Main 2015] (a) \(\mathrm{I}_{2}\)

Step-by-Step Solution

Answer

Cl2 is the most reactive.

Step 1: Understand Reactivity in Halogens

The reactivity of halogens decreases as you move down the group in the periodic table. This means that fluorine is the most reactive, followed by chlorine, bromine, and then iodine.

Step 2: Compare the Reactivity of the Given Halogens

Based on the order of reactivity in the halogens, the hierarchy is: \( \text{Cl}_2 > \text{Br}_2 > \text{I}_2 \). IC is not a halogen element, so it is not considered in the reactivity order here.

Step 3: Determine the Most Reactive Halogen

From the order established in Step 2, \(\text{Cl}_2\) is the most reactive among the given options \( \text{I}_2, \text{Cl}_2, \text{Br}_2 \).

Key Concepts

Periodic Table

The periodic table is a systematic arrangement of all known chemical elements. It was designed to illustrate recurring ('periodic') trends in the properties of elements. Elements are placed in order of increasing atomic number, which is the number of protons in the nucleus of an atom. This unique table helps chemists understand the relationships between various chemical properties of the elements.
The elements are organized into rows and columns known as periods and groups. Groups include elements that have similar reactive traits and possess a similar number of electrons in their outer shell, which leads to similar chemical behaviors. For instance, the halogens, which are the focus of this explanation, are located in Group 17. Each element in this group shares a common characteristic of having seven electrons in their valence shell, leading to a significant degree of chemical similarity among them.
Understanding the layout of the periodic table is essential as it allows chemists to predict how elements might react with each other. This prediction is based on their position on the periodic table and how they relate to others in terms of chemical reactivity and physical properties.

Chemical Reactivity

Chemical reactivity refers to how likely and how quickly an element or compound will undergo a chemical reaction with another substance. The reactivity of elements plays an essential role in understanding how substances interact and transform in chemical reactions.
Reactivity is influenced by several factors:

• Atomic size: Generally, elements with smaller atomic radii tend to exhibit higher reactivity, particularly among nonmetals.
• Electron affinity: Elements that can easily gain electrons tend to be more reactive.
• Electronegativity: Highly electronegative elements are often more reactive because they attract electrons more effectively.

When it comes to halogens, their reactivity decreases as you move down the group in the periodic table from fluorine to iodine. This pattern is due to the increasing atomic size, which makes it harder for these elements to attract additional electrons needed for chemical reactions. Therefore, chlorine is more reactive than bromine and iodine in the list, which is why it ranks highest among the given halogens in terms of reactivity.

Halogens

Halogens are a group of elements found in Group 17 of the periodic table. The name 'halogen' comes from Greek roots meaning 'salt-producing,' reflecting their ability to form salts when combined with metals. Halogens include fluorine ( ext{F} ), chlorine ( ext{Cl} ), bromine ( ext{Br} ), iodine ( ext{I} ), and astatine ( ext{At} ).
These elements are known for their high reactivity, especially with alkali and alkaline earth metals, due to their high electronegativities and electron affinities. This means they can attract electrons strongly from other elements to complete their valence shell with eight electrons, achieving a stable electronic configuration.
Among the halogens, reactivity decreases as you go down the group. Chlorine, sitting above bromine and iodine, is more reactive than both because it can more readily accept an electron to fill its outer shell. This is attributed to its smaller atomic size and higher electronegativity compared to the halogens located below it.
Halogens are also commonly used in various applications due to their reactivity, including disinfection, bleaching, and the manufacturing of certain organic compounds.