Problem 113 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the lists I and II and pick the correct matching from the codes given below: List-I A. isotope B. isobar C. isotone D. isosters E. isodiaphers List-sII (1) \({ }_{88} \mathrm{Ra}^{228}\) and \({ }_{89} \mathrm{Ac}^{228}\) (2) \({ }_{18} \mathrm{Ar}^{39}\) and \({ }_{19} \mathrm{~K}^{40}\) (3) \({ }_{1} \mathrm{H}^{2}\) and \({ }_{1} \mathrm{H}^{3}\) (4) \({ }_{92} \mathrm{U}^{235}\) and \({ }_{90}^{\mathrm{Th} 231}\) (5) \(\mathrm{CO}_{2}\) and \(\mathrm{N}_{2} \mathrm{O}\) The correct matching is: (a) \(\mathrm{A}-2, \mathrm{~B}-1, \mathrm{C}-4, \mathrm{D}-5, \mathrm{E}-3\) (b) \(\mathrm{A}-2, \mathrm{~B}-5, \mathrm{C}-1, \mathrm{D}-4, \mathrm{E}-3\) (c) \(\mathrm{A}-3, \mathrm{~B}-1, \mathrm{C}-2, \mathrm{D}-5, \mathrm{E}-4\) (d) \(\mathrm{A}-5, \mathrm{~B}-4, \mathrm{C}-1, \mathrm{D}-2, \mathrm{E}-3\) (e) \(\mathrm{A}-5, \mathrm{~B}-3, \mathrm{C}-1, \mathrm{D}-2, \mathrm{E}-4\)

Step-by-Step Solution

Answer

The correct matching is option (c).

Step 1: Understand Isotopes

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. This means they have different mass numbers. For example, \(_{1} \text{H}^{2}\) and \(_{1} \text{H}^{3}\) are isotopes because they both have 1 proton but different neutrons.

Step 2: Identify Isotopes in List II

In List II, the pair \(_{1} \text{H}^{2}\) and \(_{1} \text{H}^{3}\) both belong to hydrogen but have different mass numbers, making them isotopes. Therefore, isotope matches with (3).

Step 3: Understand Isobars

Isobars are atoms of different elements that have the same mass number. For example, \(_{88} \text{Ra}^{228}\) and \(_{89} \text{Ac}^{228}\) have different atomic numbers but the same mass number, making them isobars.

Step 4: Identify Isobars in List II

From List II, \(_{88} \text{Ra}^{228}\) and \(_{89} \text{Ac}^{228}\) are isobars as they have the same mass number (228) but different elements. Therefore, isobar matches with (1).

Step 5: Understand Isotones

Isotones are atoms of different elements with the same number of neutrons. To find isotones, calculate the number of neutrons using: Neutrons = Mass Number - Atomic Number.

Step 6: Identify Isotones in List II

Look at \(_{18} \text{Ar}^{39}\) and \(_{19} \text{K}^{40}\). Calculate neutrons: Ar has 21 (39-18) neutrons, and K has 21 (40-19) neutrons. Both have the same number of neutrons, making them isotones. So isotone matches with (2).

Step 7: Understand Isosters

Isosters are molecules or ions that have the same number of atoms and the same number of total electrons. For example, \(\text{CO}_2\) and \(\text{N}_2\text{O}\) each consist of 3 atoms.

Step 8: Identify Isosters in List II

\(\text{CO}_2\) and \(\text{N}_2\text{O}\) are isosters because both have the same number of atoms and the equivalent electronic configuration. Thus, isoster matches with (5).

Step 9: Understand Isodiaphers

Isodiaphers are atoms having nuclei that differ by a simple number of alpha particles. To identify, calculate the difference in mass number and atomic number.

Step 10: Identify Isodiaphers in List II

For \(_{92} \text{U}^{235}\) and \(_{90} \text{Th}^{231}\), they differ by 4 in both atomic and mass number, corresponding to the difference of an alpha particle (which has 2 protons and 2 neutrons), making them isodiaphers. Therefore, isodiapher matches with (4).

Step 11: Construct the Answer from Matches

From Steps 2, 4, 6, 8, and 10, we get: \(\text{A}-3\), \(\text{B}-1\), \(\text{C}-2\), \(\text{D}-5\), \(\text{E}-4\). This corresponds to option (c).

Key Concepts

Isotopes

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. This difference in neutrons means isotopes of an element have different mass numbers.
Despite these differences, isotopes exhibit similar chemical properties because they contain the same number of electrons and protons.

• An example of isotopes is the hydrogen isotopes: protium ( ({}_{1}^{1}H),
• deuterium ({}_{1}^{2}H),
• and tritium ({}_{1}^{3}H).

In the exercise, the isotopes match was (3), involving {}_{1}H^{2} and {}_{1}H^{3}, both of which are forms of hydrogen.

Isobars

Isobars are atoms of different chemical elements that share the same mass number. This occurs because they have a different number of protons and neutrons but the total sum of these two equals the same mass number.
As a result, although isobars have the same mass, their chemical properties can differ since they belong to different elements. In this exercise, the isobar pair was (1), featuring {}_{88}Ra^{228} and {}_{89}Ac^{228}. They have the same mass number of 228, despite being different elements, radium and actinium.

Isotones

Isotones are atoms from different elements that have the same number of neutrons but different numbers of protons. To identify isotones, it is vital to calculate the number of neutrons (mass number minus atomic number) and find elements that match this neutron count.
The chemical properties of isotones are usually different since they belong to distinct elements. In the given problem, the isotone pair identified was (2), where {}_{18}Ar^{39} and {}_{19}K^{40} both have 21 neutrons.

Isosters

Isosters refer to molecules or polyatomic ions that either have the same number of atoms or a similar electronic configuration. This concept focuses on the structural similarity between molecules.
For example, both CO_2 and N_2O have a total of three atoms and share a similar arrangement in terms of electrons. In the exercise, these two molecules ( (5) group) were matched as isosters due to their analogous atomic and electronic structure.

Isodiaphers

Isodiaphers are a category of nuclides that do not share the same nucleon number or atomic number but differ by a simple number of alpha particles. Here, an alpha particle consists of 2 protons and 2 neutrons.
They demonstrate how simpler components like alpha particles can be a base measure for these distinctions. In the task, (4) , capturing {}_{92}U^{235} and {}_{90}Th^{231}, were identified as isodiaphers since they differ by one alpha particle (due to their mass and atomic number differences).