Classification
Modern periodic table In the year 1913, English physicist Henry Moseley studied the wavelength of the characteristic x-rays By using different metals as anti cathode and showed that the square root of the frequency of the line is related to the atomic number. On the basis of the above observations Moseley gave the modern periodic law which states that : “Physical and chemical properties of the elements are the periodic function of their atomic numbers”. The atomic mass of an element is due to the mass of protons and neutrons present in the nucleus of its atom. Since the nucleus is located inside an atom, It is not very much linked with the properties of the element, particularly the chemical properties. These are related to the number of electrons and also the distributions of the electrons in the different energy shells. The elements with different electronic arrangements of atoms possess different chemical properties. As the number of electro...