THE MODERN PERIODIC TABLE In 1913, Henry Moseley showed that the atomic number of an element is a more fundamental property than its atomic mass as described below. Accordingly, Mendeléev’s Periodic Law was modified and atomic number was adopted as the basis of Modern Periodic Table and the Modern Periodic Law can be stated as…

Limitations of Mendeléev’s Classification Electronic configuration of hydrogen resembles that of alkali metals. Like alkali metals, hydrogen combines with halogens, oxygen and sulphur to form compounds having similar formulae, as shown in the examples here. On the other hand, just like halogens, hydrogen also exists as diatomic molecules and it combines with metals and non-metals…