What is the trend in atomic radius across a period? Down a group? Using your knowledge of atomic structure, what the explanation for this trend?
Radius increases as you go down the table and decreases as you go along,
The atomic radius along a period decreases as you are adding an electron and a proton increasing the attractive forces between the two thus the radius shrinks as the attractive force is larger.
Whilst if you down a period the electron is in a further away energy level and so the atomic radius is greater. In addition there is shielding from the energy levels in front causing the radius to be larger.