Question: how many atoms are in 3.5 moles of helium?
Answer: 023x10^23 He atoms. 1 mole Of Helium = Weight of Helium/4Weight of Helium = 1*4 = 4 grams 1 mole of Helium contains 6.023*10²³ (Avogadro number) atoms. one mole is equilant to Avogadro's number 6.02x10^23 particles.