Atomic Radius Increase Up Periodic Table: Why?

[nuby]

If an atom with more protons have tighter electron orbitals than atoms with fewer protons, why doesn't the "atomic radius" decrease up the periodic table? Instead it increases, why is this?

 

[ZapperZ]

Shielding. The inner electrons shield the nucleus from the outer electrons, so they do not have the full nuclear potential.

Furthermore, higher orbitals have very eccentric geometry which is included in what we define as the "size" of an atom.

Zz.