Modern Periodic Law

The physical and chemical properties of elements are the periodic functions of their atomic number.

Statement:

“The properties of elements are a periodic function of their atomic numbers.”

Explanation / Proof:

• When Mendeleev proposed his periodic table, the structure of the atom was not yet known.
• After the discovery of the electron, scientists began to link atomic number with the number of electrons and protons in an atom.
• In 1913, Henry Moseley used X-ray experiments to show that the atomic number (Z) equals the number of protons in an atom's nucleus.
• This showed that atomic number determines the chemical properties of elements more accurately than atomic mass.

Conclusion:

• Atomic number is the true basis for the classification of elements.
• Thus, the modern periodic table is arranged by increasing atomic number, correcting the issues in Mendeleev’s table.