Question

how does the valancy of electrons change on moving in the third periodic table

Answer 1

Hiya,
It is actually observed that the size of the atom decreases as you go from left to right in the same period (except for the last inert gas). The reason for this decrease is that; with the increased atomic number of one unit, one proton is added to the nucleus and one electron to the outer shell. The proton being ‘heavier’ than the electron, the nuclear pull on the outermost shell increases, contracting the atom slightly.