Moseley's periodic law states that the physical and chemical properties of the elements are the periodic function of their atomic numbers.
He discovered that the square root of the frequency (v) of the prominent X-rays emitted by a metal was proportional to the atomic number and not to the atomic weight of the atom of that metal.
i.e. √v = a(Z-b)
where, a is the proportionality constant and b is a constant for all the lines in given series of X-rays.
The sub-groups A and B are kept separate.
There are 18 groups.
In modern periodic table, the places of metals and non-metals are separated and there is a distinctive line of division.
Ordinary element and transition elements are separated.
Elements are arranged on the basis of electronic configuration.
Periodicity in Properties in Modern Periodic Table
lonisation Enthalpy : The minimum amount of energy required to remove an electron from an isolated gaseous atom in its ground state is called the ionisation enthalpy.
Electron gain enthalpy : When an electron is added to a gaseous atom in its ground state to convert in into a negative ion, the enthalpy change accompanying the process is called the electron gain enthalpy.
Electronegativity : It is a measure of the tendency of an atom to attract a bond pair of electrons.
Periodic Properties of the Elements
