Final answer:
Covalent radius increases as we move down a group and decreases as we move left to right across a period.
Step-by-step explanation:
Covalent radius increases as we move down a group because the n level (orbital size) increases. Covalent radius mostly decreases as we move left to right across a period because the effective nuclear charge experienced by the electrons increases, and the electrons are pulled in tighter to the nucleus.