Question

Classify nuclei. By giving example of each. Write their characteristics.

Hint:

For classifying nuclei, use the letters in the names as a mnemonic: Isotopes (same Protons), Isobars (same A - mass number), Isotones (same Neutrons).

Answer 1

Nuclei are classified based on the number of protons (atomic number, Z) and the number of neutrons (neutron number, N) they contain. The total number of protons and neutrons is the mass number (A = Z + N).
1. Isotopes \begin{itemize} \item Definition: Nuclei of the same element that have the same number of protons (same Z) but a different number of neutrons (different N), and thus a different mass number (A). \item Example: The isotopes of hydrogen are Protium (\(_{1}^{1}\text{H}\), Z=1, N=0), Deuterium (\(_{1}^{2}\text{H}\), Z=1, N=1), and Tritium (\(_{1}^{3}\text{H}\), Z=1, N=2). Another example is Carbon-12 (\(_{6}^{12}\text{C}\)) and Carbon-14 (\(_{6}^{14}\text{C}\)). \item Characteristics: Isotopes have identical chemical properties because chemical behavior is determined by the electron configuration, which depends on Z. However, they have different physical properties such as mass, density, and nuclear stability (some isotopes may be radioactive while others are stable). \end{itemize} 2. Isobars \begin{itemize} \item Definition: Nuclei of different elements that have the same mass number (same A) but different atomic numbers (different Z) and neutron numbers (different N). \item Example: Argon-40 (\(_{18}^{40}\text{Ar}\)) and Calcium-40 (\(_{20}^{40}\text{Ca}\)). Both have A=40, but Z and N are different. Another example is Carbon-14 (\(_{6}^{14}\text{C}\)) and Nitrogen-14 (\(_{7}^{14}\text{N}\)). \item Characteristics: Isobars are atoms of different elements, so they have different chemical and physical properties. \end{itemize} 3. Isotones \begin{itemize} \item Definition: Nuclei of different elements that have the same number of neutrons (same N) but different atomic numbers (different Z) and mass numbers (different A). \item Example: Chlorine-37 (\(_{17}^{37}\text{Cl}\)) and Potassium-39 (\(_{19}^{39}\text{K}\)). For both, the neutron number is N = A-Z = 20. Another example is Boron-12 (\(_{5}^{12}\text{B}\)) and Carbon-13 (\(_{6}^{13}\text{C}\)), both having N=7. \item Characteristics: Isotones are atoms of different elements, and thus they have different chemical and physical properties. \end{itemize}