Question

Isotones are the nuclides having:

• A. same mass numbers
• B. same atomic numbers
• C. same neutron number, but different atomic number
• D. different neutron number, and different mass number

Hint:

Remember the definitions: Isotopes have the same atomic number (\( Z \)), isobars have the same mass number (\( A \)), and isotones have the same neutron number (\( N = A - Z \)).

Answer 1

The Correct Option is C

Step 1: Define isotones.
Isotones are nuclides (atomic nuclei) that have the same number of neutrons but different numbers of protons (i.e., different atomic numbers). The atomic number \( Z \) is the number of protons, the mass number \( A \) is the total number of nucleons (protons + neutrons), and the neutron number \( N \) is given by \( N = A - Z \). Step 2: Analyze the options based on the definition.
- (A) Same mass numbers: Nuclides with the same mass number \( A \) are called isobars (e.g., \(^{14}\text{C}\) and \(^{14}\text{N}\), both with \( A = 14 \)). This is incorrect for isotones.
- (B) Same atomic numbers: Nuclides with the same atomic number \( Z \) are isotopes (e.g., \(^{12}\text{C}\) and \(^{14}\text{C}\), both with \( Z = 6 \)). This is incorrect for isotones.
- (C) Same neutron number, but different atomic number: This matches the definition of isotones. For example, \(^{14}\text{C}\) (\( Z = 6, N = 14 - 6 = 8 \)) and \(^{15}\text{N}\) (\( Z = 7, N = 15 - 7 = 8 \)) are isotones because they have the same neutron number (\( N = 8 \)) but different atomic numbers (\( Z = 6 \) and \( Z = 7 \)).
- (D) Different neutron number, and different mass number: This does not describe isotones, as isotones must have the same neutron number. Step 3: Confirm the correct option.
Isotones are defined by having the same neutron number \( N \) but different atomic numbers \( Z \), which matches option (C).