Describe and explain how

Question

1.Atomic radius changes across a period and how atomic radius changes down the group

Answer 1

The atomic radius decreases moving from left to right across a period, and moving up within a group.

Explanation:  As you move left to right in a period, the energy level of the valence electrons remains the same, but the number of protons in the nucleus increases.  Thus, the valence electrons are the same distance from the nucleus, but the they are pulled stronger by the protons, making the radius smaller.  Going down within a group, the energy level of the valence electrons increases, meaning they get further away from the nucleus. Thus, the radius increases (meaning it decreases moving up in a group).