The atomic number is considered more preferable and fundamental than atomic mass for several reasons:
Unique Identification: Each element has a unique atomic number, which corresponds to the number of protons in its nucleus. This characteristic allows elements to be unequivocally identified and organized on the periodic table. Atomic numbers provide a consistent and reliable means of distinguishing one element from another.
Periodic Table Organization: The periodic table is arranged based on atomic number, with elements ordered in ascending order of their atomic numbers. This arrangement reflects the periodicity and trends in element properties, such as chemical reactivity, atomic size, and electron configuration. Atomic number-based organization provides a logical framework for understanding the relationships between elements.
Consistency and Stability: The atomic number is a fundamental property of an element that remains constant for a given element. It is not affected by isotopic variations, which can impact atomic mass. In contrast, atomic mass may vary due to the existence of different isotopes, each with its own mass. However, the atomic number always stays the same, regardless of the isotope.
Nuclear Stability and Chemical Behavior: The atomic number determines an element's position in the periodic table, which in turn influences its electron configuration and chemical behavior. Changes in atomic mass due to different isotopes do not significantly impact an element's chemical properties. Instead, it is the number of protons (atomic number) that primarily governs an element's behavior and reactivity.
Precision and Accuracy: Atomic numbers are integers and provide a precise and unambiguous measure of an element's identity. In contrast, atomic masses can be decimal values due to the average mass calculations considering isotopic abundances. Atomic masses are valuable for more detailed calculations involving stoichiometry or isotopic compositions, but atomic numbers offer a simpler and more straightforward identification system.
While atomic mass has its own importance, particularly in isotopic studies and mass spectrometry, the atomic number is the preferred and standardized parameter for identifying and organizing elements in the field of chemistry. Its consistent and unique nature makes it more reliable and widely used in scientific contexts.