How many atoms in 3 moles of helium?

There are 1.8066 x 10 ^24 atoms in 3 moles of helium

1 mole of any substance is equal to 6.022 × 1023 atoms , This is called the  Avogadro's Number and it represents 12 grams of pure carbon.

Hence,

I mole of Helium = 6.022 × 1023 atoms

Therefore,  

3 moles of helium will be 3 x   6.022 × 1023 atoms

3 moles of helium =1.8066 x 10 ^24 atoms

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NA = 6.02214076×10^23 mol−1.

Explanation:

1 mole of helium gas contains 6.02 x10^23 helium atoms. So multiply this by 3 after solving the equation.