Understanding Element Classification by Atomic Number

Chemists have developed various ways to classify elements to better understand their properties and relationships. These classifications evolved over time as scientists discovered more elements and learned more about their fundamental characteristics. The basis of classification changed significantly with new scientific understanding.

Basis of Different Periodic Classifications

Let's examine the basis for each classification method mentioned in the options:

• Modern Periodic Table: This classification is based on the atomic number of elements. The Modern Periodic Law states that the properties of elements are a periodic function of their atomic numbers. Elements are arranged in increasing order of their atomic numbers in periods and groups.
• Mendeleev's Periodic Table: Dmitri Mendeleev's classification was primarily based on atomic mass. His Periodic Law stated that the properties of elements are a periodic function of their atomic masses. He also considered the chemical properties of elements for arrangement.
• Dobereiner's Law of Triads: Johann Wolfgang Dobereiner grouped elements into sets of three, called triads, based on similar chemical properties. In a triad, the atomic mass of the middle element was approximately the average of the atomic masses of the other two elements. This classification used atomic mass and properties.
• Newlands Law Of Octaves: John Newlands arranged elements in increasing order of their atomic masses and observed that the properties of every eighth element were similar, like the notes in a musical octave. This classification was based on atomic mass and properties.

Identifying Classification Based on Atomic Numbers

Comparing the bases of these classifications, it is clear that the Modern Periodic Table is the only one listed that uses the atomic number as the fundamental property for arranging elements. The shift from atomic mass to atomic number as the basis for the periodic table was a crucial development, resolving anomalies present in earlier classifications like Mendeleev's.

Conclusion

Based on the analysis of different classification methods, the Modern Periodic Table is the classification that is based on atomic numbers.

Revision Table: Key Periodic Classification Concepts

Additional Information: The Significance of Atomic Number

The discovery of the concept of atomic number and its link to the number of protons by Henry Moseley around 1913 provided the correct fundamental basis for arranging elements. Arranging elements by atomic number perfectly aligned with the observed chemical and physical properties and resolved the issues that arose when elements were arranged strictly by atomic mass. The Modern Periodic Table, built upon the atomic number, is the universally accepted framework for studying elements today.