The atomic weight of oxygen is 15.999 grams/mole. Each mole has a number of atoms equal to the Avogadro constant, ≈6.022*1023. So, 4 grams of oxygen is
4 g/(15.999 g/mol) = .250 mol = .25*6.022*1023 atoms = 1.506*1023 atoms.
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Since we're counting atoms, it matters not that they happen to be clumped into O2. An atom of oxygen weighs the same whether it is part of O2 or not.
4 g/(15.999 g/mol) = .250 mol = .25*6.022*1023 atoms = 1.506*1023 atoms.
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Since we're counting atoms, it matters not that they happen to be clumped into O2. An atom of oxygen weighs the same whether it is part of O2 or not.
