Question

What is the cause of periodicity of elements in the Periodic table?

Answer 1

1. Modern periodic table is the arrangement of elements on the basis of increasing atomic number in 7 horizontal rows and 18 vertical columns.
2. Horizontal rows are termed as Periods while the vertical columns are termed as Groups.
3. Since elements in the periodic table are arranged on the basis of atomic number or electronic configuration, the elements with the same valence electron lie in the same Group.
4. Various properties like atomic size and ionization energy of the elements rely on the valence electrons and therefore, these properties exhibit a regular change on moving down the Group or across the Period. These properties are termed as periodic properties and this regular change is termed as periodicity.
5. Due to the presence of the same valence electrons in the Group and an increase in the valence electrons by 1 on moving left to right, the periodicity in the periodic table occurs.