Final answer:
The statement is false; bromine has a smaller atomic radius than selenium, despite having more protons, due to stronger nuclear charge attraction within the same electron shell period. Bromine and selenium belong to different groups, and atomic radius increases as you move down a group in the periodic table.
Step-by-step explanation:
The statement that bromine has a larger atomic radius than selenium because it has the same number of electron shells but more protons is false. In the periodic table, elements are arranged in rows called periods which correspond to the number of electron shells. Within a period, as the number of protons increases, the atomic radius generally decreases due to the increased nuclear charge pulling the electron shells closer. This explains why bromine, which has more protons than selenium, actually has a smaller atomic radius compared to selenium.
All halogens, like bromine, have seven electrons in their valence shell (ns²np⁵) and are known for forming diatomic molecules such as Br₂. Unlike the trend described for increasing atomic number within a period, the atomic radius within a group increases with an increase in atomic number. This is due to the addition of electron shells which outweigh the effect of increasing nuclear charge.
This trend is evident when we consider the physical states of halogens at room temperature. For example, fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid, demonstrating the increase in atomic radius and subsequently intermolecular dispersion forces down the group.