Question

What is the cause of periodicity?

Answer 1

1. The main cause of the periodicity of elements in the modern periodic table is the valence electrons.
2. Valence electrons are the electrons which are present in the last shell of the atom.
3. The elements which have the same number of valence electrons have similar chemical properties.
4. Elements of the same valence electron reoccur after a fixed interval which causes the periodicity in the properties of elements.