Question

why does atomic radius decrease as we move from left to right now period

Answer 1

Moving from left to right across a period atomic radius decreases, the nucleus of the atom gains protons moving left to right increasing the positive charge of the nucleus and increasing the attractive force of the nucleus upon the electrons......

Answer 2

This causes the electron to movecloser to the nucleus, thus increasing the electron affinity from left to rightacross a period. Electron affinity increases from left to right within aperiod. This is caused by the decreasein atomic radius.