Problem 101 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following: List I element with highest electronegativity 2- element with highest electron affinity 3\. liquid non metal 4\. metallic solid List II (i) \(\mathrm{I}_{2}\) (ii) \(\mathrm{Br}_{2}\) (iii) \(\mathrm{Cl}_{2}\) (iv) \(\mathrm{F}_{2}\) The correct matching is: $$ \begin{array}{|c|c|c|c|c|} \hline & 1 & 2 & 3 & 4 \\ \hline \mathrm{a} & \text { (iii) } & \text { (ii) } & \text { (i) } & \text { (iv) } \\ \hline \mathrm{b} & \text { (iv) } & \text { (iii) } & \text { (i) } & \text { (ii) } \\ \hline \mathrm{c} & \text { (ii) } & \text { (iii) } & \text { (iv) } & \text { (i) } \\ \hline \mathrm{d} & \text { (i) } & \text { (ii) } & \text { (iii) } & \text { (iv) } \\ \hline \end{array} $$

Step-by-Step Solution

Answer

The correct matching is option b: (iv), (iii), (ii), (i).

Step 1: Identify Highest Electronegativity

In the periodic table, fluorine (F_{2}) is the element with the highest electronegativity. Therefore, match "element with highest electronegativity" to (iv) \( \mathrm{F}_{2} \).

Step 2: Identify Highest Electron Affinity

The element with the highest electron affinity from the options given is chlorine (Cl_{2}). Match "element with highest electron affinity" to (iii) \( \mathrm{Cl}_{2} \).

Step 3: Identify Liquid Non-Metal

Among the halogens provided, \(\mathrm{Br}_{2}\), bromine, is a liquid at room temperature. Therefore, match "liquid non-metal" to (ii) \( \mathrm{Br}_{2} \).

Step 4: Identify Metallic Solid

The list provided doesn't include a metallic solid. However, non-metallic iodine is often used in a solid crystalline form; therefore, match "metallic solid" to (i) \( \mathrm{I}_{2} \), the closest option given the limited choices and no metallic element listed.

Key Concepts

Electronegativity

Electronegativity is a chemical property that describes the ability of an atom to attract electrons towards itself. In the periodic table, electronegativity generally increases across a period from left to right and decreases down a group. This means that the most electronegative elements are found in the upper right corner of the periodic table, excluding the noble gases.
Fluorine is the most electronegative element, with a value of 3.98 on the Pauling scale, making it highly effective at attracting electrons in chemical bonds.

• Electronegativity depends on atomic number and the distance of the electrons in the outer shell from the nucleus.
• It is important in determining bond polarity and the type of bond that forms between two atoms.
• Higher electronegativity means a stronger pull on shared electrons.

Electron Affinity

Electron affinity is the amount of energy released when an electron is added to a neutral atom, forming a negative ion. It measures the tendency of an atom to gain an electron. Like electronegativity, electron affinity typically increases across a period and decreases down a group in the periodic table.
Chlorine has the highest electron affinity among the elements because it releases a significant amount of energy when gaining an electron, which stabilizes the atom.

• Electron affinity is a quantitative measure often expressed in kilojoules per mole (kJ/mol).
• It is a key factor in determining how elements form ions and compounds.
• High electron affinity values indicate a strong desire to gain extra electrons.

Liquid Non-Metals

At room temperature, most non-metals exist in a gaseous or solid state, with only bromine (\(\mathrm{Br}_{2}\) occurring naturally as a liquid. This is due to its larger atomic size and weak intermolecular forces compared to its halogen relatives, fluorine and chlorine, which are gases at room temperature.
Bromine's distinct properties and intermediate electronegativity make it a unique member of the halogen group.

• Liquid non-metals are rare and usually involve elements with intermediate atomic sizes.
• The existence of liquid non-metals is due to balances between atomic size, electron arrangement, and intermolecular forces.
• Bromine is notable for its deep reddish-brown color and high density among non-metals.

Metallic Solids

Although none of the elements listed in the exercise are true metallic solids, the term typically refers to the solid structure characterized by metallic bonding, where free electrons allow for conductivity and malleability.
Iodine (\(\mathrm{I}_{2}\)) is sometimes confused as a metallic solid in some contexts because it forms a crystalline solid at room temperature. However, it lacks free electrons necessary for metallic properties like electricity conductance.

• Metallic solids usually consist of closely packed atoms in a lattice-like structure.
• These solids exhibit properties such as electrical conductivity, malleability, and luster.
• Iodine's solid form, being a molecular solid, should not be mistaken for a true metallic solid.