# Why do atomic radii decrease across a period? [closed]

It's said that atomic size/radius decreases across a period, in spite of addition of electrons. But how does this actually work?

Atomic radius decreases across a period because electrons are being added to the same energy level and at the same time the nucleus is increasing in protons. The increase in nuclear charge $$Z_{eff}$$ attracts the electrons more strongly, (addition of one proton has a greater effect than addition of 1 electron) thus pulling electron closer to the nucleus and making atomic radius decrease.