Final answer:
The atom with the largest covalent radius between the given electron configurations (1s¹ and 1s² 2s¹) is lithium, represented by the configuration B) 1s² 2s¹, due to its additional energy level.
Step-by-step explanation:
The atom with the electron configuration 1s² 2s¹, which represents lithium, will have the largest covalent radius when compared to the atom with the electron configuration 1s¹ (hydrogen). As atoms increase in electron configuration and thus atomic number, the distance from the nucleus to the valence electrons generally increases, leading to a larger covalent radius. However, as you move from left to right across a period, despite increases in atomic number, the covalent radius usually decreases due to the increase in nuclear charge pulling electrons closer to the nucleus. In this case, lithium (1s² 2s¹) has a larger covalent radius than hydrogen (1s¹) because it has an additional energy level that increases the distance of the valence electron shell from the nucleus.