Problem 28 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The triad of nuclei that is isotonic is (a) \({ }_{6}^{14} \mathrm{C},{ }_{7}^{15} \mathrm{~N},{ }_{9}^{17} \mathrm{~F}\) (b) \({ }_{6}^{12} \mathrm{C},{ }_{7}^{14} \mathrm{~N},{ }_{9}^{19} \mathrm{~F}\) (c) \({ }_{6}{\underline{\phantom{xx}}}^{14} \mathrm{C},{ }_{7}^{14} \mathrm{~N},{ }_{9}^{17} \mathrm{~F}\) (d) \({ }_{6}^{14} \mathrm{C},{ }_{7}^{14} \mathrm{~N},{ }_{9}^{19} \mathrm{~F}\)

Step-by-Step Solution

Answer

The isotonic triad is option (a): \( {}_{6}^{14} \text{C}, {}_{7}^{15} \text{N}, {}_{9}^{17} \text{F} \).

Step 1: Understanding Isotones

Isotones are atoms of different elements that have the same number of neutrons. To determine if nuclei are isotonic, we need to calculate the number of neutrons in each nucleus and check if they match.

Step 2: Calculate Neutrons for Option (a) - \( \text{C}, \text{N}, \text{F} \)

For \( {}_{6}^{14} \text{C} \), the number of neutrons = 14 - 6 = 8.\For \( {}_{7}^{15} \text{N} \), the number of neutrons = 15 - 7 = 8.\For \( {}_{9}^{17} \text{F} \), the number of neutrons = 17 - 9 = 8.\All three nuclei have 8 neutrons.

Step 3: Evaluate the Remaining Options

For option (b):\- \( {}_{6}^{12} \text{C} \): Neutrons = 12 - 6 = 6.\- \( {}_{7}^{14} \text{N} \): Neutrons = 14 - 7 = 7.\- \( {}_{9}^{19} \text{F} \): Neutrons = 19 - 9 = 10.\Neutron counts are 6, 7, and 10, so they aren’t identical.\For option (c):\- \( {}_{6}^{14} \text{C} \): Neutrons = 14 - 6 = 8.\- \( {}_{7}^{14} \text{N} \): Neutrons = 14 - 7 = 7.\- \( {}_{9}^{17} \text{F} \): Neutrons = 17 - 9 = 8.\Neutron counts are 8, 7, and 8, so they aren’t identical.\For option (d):\- \( {}_{6}^{14} \text{C} \): Neutrons = 14 - 6 = 8.\- \( {}_{7}^{14} \text{N} \): Neutrons = 14 - 7 = 7.\- \( {}_{9}^{19} \text{F} \): Neutrons = 19 - 9 = 10.\Neutron counts are 8, 7, and 10, so they aren’t identical.

Step 4: Conclusion Based on Calculations

Option (a) has the same number of neutrons (8) for all nuclei and is the correct isotonic triad.

Key Concepts

Atomic Structure

Atoms are the building blocks of matter and have a detailed structure governing their behavior and properties. Every atom consists of three main subatomic particles: protons, neutrons, and electrons, each playing a crucial role.

• Protons: These positively charged particles are found within the atomic nucleus. The number of protons defines the element and is known as the atomic number.
• Neutrons: These are neutral particles with no charge, also located in the nucleus. Neutrons add mass to the atom and influence its stability.
• Electrons: Negatively charged particles that orbit the nucleus, involved primarily in chemical reactions.

The nucleus, composed of protons and neutrons, is tiny compared to the overall atom but contains almost all its mass. The number of electrons equals the number of protons in a neutral atom. The atomic structure is essential for determining the atom's characteristics, including its reactivity and bonding capabilities.
Understanding the atomic structure helps explain the formation and nature of different atoms, isotopes, and isotones.

Neutron Calculation

Calculating the number of neutrons in an atom is straightforward. It's an essential step in identifying isotones.

• To find the neutrons, subtract the atomic number (protons) from the atomic mass (total of protons and neutrons).

For example, take the carbon isotope \[{}_{6}^{14} ext{C}\]. The atomic number is 6, indicating 6 protons. The atomic mass is 14.
Subtract the atomic number from the atomic mass to determine the number of neutrons: \[14 - 6 = 8 \]. This straightforward calculation allows for the comparison of different nuclei to determine if they have the same number of neutrons, classifying them as isotones if they do. Understanding neutron calculation can reveal a lot about an atom's stability and decay properties, further connecting to the broader field of nuclear chemistry.

Nuclear Chemistry

Nuclear chemistry focuses on the reactions and properties of atomic nuclei. These reactions are fundamental in power generation and understanding the universe's elemental composition. The stability of an atom's nucleus depends largely on the balance between protons and neutrons.

• Isotopes: Variants of an element with different numbers of neutrons but the same number of protons.
• Isotones: Nuclei with the same number of neutrons, such as the example given in the exercise, highlight important nuclear reactions and stability properties.

Nuclear chemistry is also crucial for applications like nuclear reactors, where careful neutron manipulation is necessary to sustain fission reactions. Moreover, it plays a role in medical fields, from imaging techniques to cancer treatments. Understanding nuclear chemistry not only helps in the practical applications but also in exploring new research areas, such as nuclear energy development and radioactive waste reduction.