Problem 167 - A Complete Resource Book in Chemistry for JEE Main

Question

Of the following sets which one does not contain iso electronic species? (a) \(\mathrm{PO}_{4}^{3-}, \mathrm{SO}_{4}^{2-}, \mathrm{ClO}_{4}^{-}\) (b) \(\mathrm{CN}^{-}, \mathrm{N}_{2}, \mathrm{C}_{2}^{2-}\) (c) \(\mathrm{SO}_{3}^{2-}, \mathrm{CO}_{3}^{2-}, \mathrm{NO}_{3}^{-}\) (d) \(\mathrm{BO}_{3}{\underline{\phantom{xx}}}^{3}, \mathrm{CO}_{3}{\underline{\phantom{xx}}}^{2}-\mathrm{NO}_{3}^{-}\)

Step-by-Step Solution

Answer

Set (d) does not contain isoelectronic species.

Step 1: Understanding Isoelectronic Species

Isoelectronic species are ions, atoms, or molecules that have the same number of electrons. In order to identify if a set contains isoelectronic species, we need to count the total number of electrons in each species within the set and see if they match.

Step 2: Calculating Electrons in Set (a)

For each ion, calculate the total number of electrons: - - P: 15, O: (4×8), charge: +3, total = 32 - S: 16, O: (4×8), charge: +2, total = 32 - Cl: 17, O: (4×8), charge: +1, total = 32 All species in set (a) have 32 electrons.

Step 3: Calculating Electrons in Set (b)

For each species, calculate the number of electrons: - - C: 6, N: (6+7), charge: +1, total = 14 - N₂: 14 electrons total. - - C: 6, total = 14 All species in set (b) have 14 electrons.

Step 4: Calculating Electrons in Set (c)

For each ion, calculate the total number of electrons: - - S: 16, O: (3×8), charge: +2, total = 32 - C: 6, total = 32 - N: 7, total = 32 All species in set (c) have 32 electrons.

Step 5: Calculating Electrons in Set (d)

For each ion, calculate total number of electrons: - - B: 5, O: (3×8), total = 29 - C: 6, total = 32 - N: 7, total = 32 Species in set (d) have different number of electrons: 29 for the first, 32 for others.

Step 6: Determining Which Set Is Not Isoelectronic

After finding the electron count for each set's species, sets (a), (b), and (c) contain isoelectronic species. Set (d) does not have all species with the same electron count; thus, it does not contain isoelectronic species.

Key Concepts

Electron Counting

Electron counting is a fundamental technique in chemistry used to determine the number of electrons present in an atom, ion, or molecule. This is crucial for identifying isoelectronic species. Isoelectronic species share the same number of total electrons even if they differ in their nuclear or elemental composition. By counting electrons, we can predict or verify the properties of chemical species and determine their potential reactions.

To perform electron counting, follow these simple steps:

• Identify the atomic numbers for each element in the chemical species. This value indicates how many protons (and therefore electrons in a neutral atom) are present.
• Add up the electrons according to the chemical formula, considering any charges. If an ion carries a negative charge, add extra electrons equal to the charge. If it’s positive, subtract accordingly.

This counting method provides a straightforward way to compare different chemical entities, assess their bonding capabilities, and deduce structural similarities. Consistent application of electron counting is central to solving chemical problems effectively.

Chemical Species

Chemical species refer to different forms of atoms, molecules, ions, or radicals distinguished by their distinct chemical identity. These species play vital roles in chemical reactions and interactions. Understanding chemical species is essential in comparing and contrasting different molecules or ions, particularly when examining isoelectronic species.

When analyzing chemical species:

• Consider valence electrons, as they are key players in chemical bonding.
• Examine how atoms are arranged and how electrons are distributed in molecules or ions.
• Look at the charge of ions—positive ions have fewer electrons than their neutral counterparts, while negative ions have more.

Recognizing and distinguishing chemical species by their electron configurations and arrangement can help predict their behavior in chemical reactions. This makes understanding chemical species a fundamental aspect of studying chemistry.

Ion Comparison

Ion comparison involves analyzing different ions in terms of their electron configurations and charges. This is pivotal when determining whether a group of ions or molecules is isoelectronic, meaning they share the same number of electrons.

To compare ions effectively, observe these points:

• Compare the total number of electrons in each ion; this involves both the atomic numbers and any charges related to the ion.
• Evaluate the impact of added or removed electrons, which affects not only the electron count but also the structural and reactive properties of ions.
• Check if different ions mimic each other by having the same electron numbers, even though they originate from different elements.

Understanding ion comparison is crucial in chemical problem solving, helping to predict reactivity and compatibility between different chemical species. It's all about finding a common electron ground among different species.

Chemical Problem Solving

Chemical problem solving is an intricate process that involves tackling problems by understanding and applying various chemical principles. When it comes to isoelectronic species, problem solving is really about comparing and counting electrons to ascertain relationships between different species.

For effective chemical problem solving:

• Start by identifying what is being asked, such as determining whether given sets of species are isoelectronic.
• Break down the species into their elemental components and perform electron counting for each.
• Compare the total electron count across different species to identify isoelectronic groups.

Chemical problem solving often requires a keen understanding of different chemical properties and observational skills to recognize patterns and derivations. Mastering these skills ensures efficient and correct solutions in chemistry exercises.