Problem 156 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following: List I (Compound) 1\. \(\mathrm{XeF}_{2}\) 2\. \(\mathrm{XeF}_{4}\) 3\. XeF 4\. \(\mathrm{XeO}_{3}\) List II (Number of lone pair electron) (i) 0 (ii) 1 (iii) 2 (iv) 3

Step-by-Step Solution

Answer

1 matches (iv), 2 matches (iii), 3 - typically not considered, 4 matches (ii).

Step 1: Understanding the relationship

Identify that the relationship is between the chemical compound of Xenon and its corresponding number of lone pair electrons.

Step 2: Analyzing XeF_2

The compound XeF_2 contains Xenon (Xe) with a total of 8 valence electrons. Two of these electrons are shared with two Fluorine atoms, leaving 6 electrons. These 6 electrons form 3 lone pairs.

Step 3: Analyzing XeF_4

For XeF_4, Xenon shares 4 electrons with 4 Fluorine atoms, leaving 4 electrons. These 4 electrons make up 2 lone pairs.

Step 4: Analyzing XeF

The existence of XeF is practically not known because Xe typically forms stable compounds with 2 or more Fluorine atoms. If assuming XeF formation, one fluorine would share 2 of Xe's electrons, leaving the Xe with 6 electrons, suggesting 3 lone pairs, but XeF does not practically exist.

Step 5: Analyzing XeO_3

In XeO_3, Xenon shares 6 electrons with 3 Oxygen atoms (2 electrons per bond). This leaves 2 electrons, forming 1 lone pair.

Step 6: Match Results

1. XeF_2 has 3 lone pairs, matching with (iv). 2. XeF_4 has 2 lone pairs, matching with (iii). 3. XeF - usually does not exist (assumed 3 lone pairs or impractical). 4. XeO_3 has 1 lone pair, matching with (ii).

Key Concepts

Valence Electrons

Valence electrons are the electrons present in the outermost shell of an atom. These electrons play a crucial role in determining how an atom will interact and bond with other atoms. In the case of xenon (Xe), it is a noble gas with a total of 8 valence electrons.

• Xenon typically doesn't react easily because noble gases are known for their stability due to their full valence shells.
• However, under certain conditions, xenon can form compounds by sharing or transferring these valence electrons to form bonds.

In compounds like XeF_2 and XeF_4, xenon's valence electrons are shared with fluorine atoms, resulting in stable molecular structures.

Lone Pairs

Lone pairs refer to electron pairs in the valence shell of an atom that are not involved in chemical bonding. They hold a significant role in determining the geometry and reactivity of molecules.
For xenon compounds:

• In XeF_2, after sharing electrons with fluorine, xenon retains 3 lone pairs.
• In XeF_4, the sharing leaves xenon with 2 lone pairs.
• In XeO_3, xenon has 1 lone pair remaining after forming bonds with oxygen.

The presence and arrangement of these lone pairs significantly influence the molecular shape and the compound's properties.

Fluorine Compounds

Fluorine is one of the most electronegative elements, often forming strong bonds with other elements. In the case of xenon-fluorine compounds, fluorine's high reactivity plays a critical role.

• Combinations like XeF_2 and XeF_4 are possible due to fluorine's ability to influence xenon's electrons to form stable complexes.
• The strength of the xenon-fluorine bond is a result of this electronegativity which leads to a robust sharing of electrons.

Fluorine's unique properties enable it to help form compounds with even gases like xenon, which are otherwise quite non-reactive.

Oxidation States

Oxidation states indicate the degree of oxidation (loss of electrons) an atom has in a compound. Particularly for xenon, which usually exhibits multiple oxidation states in its compounds, understanding these is crucial.

• In XeF_2 and XeF_4, xenon exhibits oxidation states of +2 and +4 respectively.
• For XeO_3, xenon typically achieves an oxidation state of +6.

These varying oxidation states stem from xenon's ability to engage its outer electrons in bonding, despite its position as a noble gas. Understanding these states is essential for predicting the chemical behavior and interactions of xenon compounds.