Final answer:
As you move across a period of the periodic table (from left to right), the atomic radius decreases, and as you move down a group (top to bottom), the atomic radius increases. The atomic radii are generally smaller the further up and to the right of the periodic table.
Step-by-step explanation:
The atomic radius is an important atomic property that refers to a measure of an atom's size. There is a clear trend observed in the atomic radii as we move across and down the periodic table. When considering the trend across a period (from left to right) of the periodic table, the atomic radii generally decrease. This is because, as the atomic number increases, the number of protons in the nucleus also increases, creating a stronger pull on the electron cloud, which brings it closer to the nucleus, resulting in a smaller atomic radius.
Conversely, when moving down a group (from top to bottom), the atomic radii increase. This is because with each successive element down a group, an additional electron shell is added, and the outermost electrons are found in a shell with a larger principal quantum number, making them physically farther from the nucleus.
Therefore, the answer to the multiple-choice question is that the further up and to the right of the periodic table, the smaller the atomic radius (generally).