9) An atom with an atomic radius smaller than that of sulfur (S) is __________.A.) Oxygen (O)B.) Chlorine (Cl)C.) Calcium (Ca)D.) Lithium (Li)E.) None of the above

The atomic radius of an atom generally increases as you move down a group (column) and decreases as you move across a period (row) from left to right on the periodic table.

Sulfur (S) is in the 3rd period and 16th group.

A.) Oxygen (O) is in the 2nd period and 16th group. Because it is in the same group but a higher period, it is smaller than sulfur.

B.) Chlorine (Cl) is in the 3rd period and 17th group. Because it is in the same period but a higher group, it is smaller than sulfur.

C.) Calcium (Ca) is in the 4th period and 2nd group. Because it is in a lower period and group, it is larger than sulfur.

D.) Lithium (Li) is in the 2nd period and 1st group. Because it is in a higher period and group, it is larger than sulfur.

Therefore, the answer is A.) Oxygen (O) and B.) Chlorine (Cl).