Answer:
Atomic radii tend to decrease from left to right across a period and increase from top to bottom within a group.
This is because as you move from left to right across a period, the number of protons in the nucleus increases, but the number of electron shells remains the same. This means that the electrons are pulled closer to the nucleus, and the atomic radius decreases. As you move from top to bottom within a group, the number of electron shells increases, while the number of protons in the nucleus remains the same. This means that the electrons are further away from the nucleus, and the atomic radius increases.
Step-by-step explanation: