Why Sodium and phosphorus are in the same period, but they have different atomic radii?

This has nothing to do with school. i wrote a poem to my crush, who i'm asking out soon. tell me if it's cheesy, or cute. "roses are red, violets are blue no love story sounds right if it doesn't include you. dance with me all night, gaze into my eyes i'll hand you my heart, as well as my pride. when i hear your name, my heart goes insane. your all that i want, all that i need promise me you'll stay with me. here it is the final line, jasmine hill will you be mine? " i'm also going to buy her flowers, teddy bear and some food lol. written by me, bre (: