The modern periodic table was developed by Dmitri Mendeleev, a Russian chemist, in 1869.
- Mendeleev arranged the known elements in order of increasing atomic mass and noticed a repeating pattern of chemical properties.
- He left gaps for undiscovered elements and even predicted their properties with remarkable accuracy (for example, gallium and germanium).
- Later, in 1913, Henry Moseley, a British physicist, refined the table by arranging elements according to their atomic number (the number of protons), which resolved inconsistencies in Mendeleev’s version.
So, Mendeleev is credited with creating the modern periodic table, while Moseley’s work gave it its current scientific foundation.