Final answer:
As the atomic number of the elements in Period 2 increases, the nuclear charge of each successive atom increases, and the covalent radius increases.
Step-by-step explanation:
As we move across Period 2 of the periodic table from left to right, the atomic number of the elements increases. This means that the number of protons in the nucleus, and thus the nuclear charge, increases as well. At the same time, the valence electron shell remains the same, but the principal quantum number increases. Therefore, as we move across Period 2, the atomic radius decreases due to the increasing nuclear charge capturing the valence electrons more tightly.
However, as we move down a group in the periodic table, the atomic radius increases. This is because the valence electron shell gets larger and is located farther away from the nucleus. The principal quantum number also increases as we move down a group, which contributes to the larger atomic radius. Therefore, the trend in Period 2 is that the nuclear charge of each successive atom increases, and the covalent radius increases.