Final answer:
The noble gas from Group 18 in the periodic table having a density of 5.857 8/L at 0°C and 1 atm is Radon (Rn).
Step-by-step explanation:
The noble gases (Group 18 in the periodic table) are known for their low reactivity due to their complete valence electron shells. They include Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn). The density of a substance can be a helpful property in identifying it. You mentioned a gas with a density of 5.857 8/L at 0°C and 1 atm. After cross-referencing this information with known densities of noble gases at standard conditions, the noble gas with this density is Radon (Rn).
Learn more about Noble Gases