Which of the following gases contains the highest number of atoms at s.t.p?

The gas that contains the highest number of atoms at standard temperature and pressure (s.t.p) is the gas with the highest number of moles. Neon is a noble gas that exists as single atoms and has an atomic number of 10. Therefore, 6 moles of neon would contain 6 times Avogadro's number (6.02 x 10^23) of atoms, making it the gas with the highest number of atoms at s.t.p. Oxygen exists as a diatomic molecule (O2), so 3 moles of oxygen would contain 3 times Avogadro's number of molecules, which is half the number of atoms in 6 moles of neon. Chlorine is a diatomic molecule like oxygen, but its atomic number is 17, which is higher than that of oxygen. However, 2 moles of chlorine would still contain fewer atoms than 6 moles of neon. Ethane (C2H6) is a compound made up of multiple atoms, so 1 mole of ethane would contain fewer atoms than any of the other options. Therefore, the gas that contains the highest number of atoms at s.t.p is 6 moles of neon.