Final answer:
Without calculations, 1-gram samples of lithium, iron, and uranium can be compared by molar mass. Lithium, having the lowest molar mass, contains the most atoms per gram. Hence, 1 gram of lithium has the most atoms compared to 1 gram of iron or uranium.
Step-by-step explanation:
To determine which sample contains the most atoms without doing any calculations, we can rely on the concept of molar mass and Avogadro's number. Each element has a specific molar mass, which is the mass of one mole of that element's atoms, where one mole equals 6.022 × 1023 atoms. Lithium has a much lower molar mass compared to iron or uranium; therefore, for the same mass (1 gram), lithium will contain the most moles of atoms, and hence, the most atoms.
To elaborate, the molar mass of lithium (Li) is approximately 6.94 g/mol, iron (Fe) is about 55.85 g/mol, and uranium (U) is roughly 238.03 g/mol. Given that 1 gram of each element is being considered, lithium with the lowest molar mass will have the highest number of moles and therefore the highest number of atoms, as dictated by Avogadro's number.