Aprism refracts white light into rainbow colors because

Because each color is refracted differently, each bends at a different angle, resulting in a fanning out and separation of white light into the colors of the spectrum. Water droplets in the air can act in a manner similar to that of a prism, separating the colors of sunlight to produce a spectrum known as a rainbow.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.