Question

Explain, in detail, why atomic radii do not increase uniformly with increasing atomic number. Give specific examples in your answer.

Answer 1

The electrons orbiting the nucleus are in shells that only hold so many electrons. When a shell is full, adding another electron adds into another shell to the atom, this causes a large increase in atomic radii.On going down a group (For example IA group elements Li,, Na, K,Rb Cs,Fr) the atoms get bigger because you are adding another shell of electrons.While going across a period (for example 3rd period Na, Mg, Al etc (except for the noble gases) ) the atomic number is increasing since the number of protons that attract the electrons) and pulling the electrons inwards so that decreasing the radius.