By definition one gram-mole of a substance contains (approximately) 6x1023 atoms (this is known as Avogadro's number or Avogadro's constant).
The atomic weight of silicon is 28, so Avogadro's number of silicon atoms weigh 28 grams. Therefore 1 atom of silicon weighs (28/Avogardo's number) grams.
Do a search on Avogadro's number to find a more accurate value than I've used here; and search on atomic weight of silicon to find the value of 28.
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6x1023 atoms of silicon weigh 28 grams, so one atom of silicon weighs 28x10-23/6 grams ≈ 4.7x10-23 grams
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By definition one gram-mole of a substance contains (approximately) 6x1023 atoms (this is known as Avogadro's number or Avogadro's constant).
The atomic weight of silicon is 28, so Avogadro's number of silicon atoms weigh 28 grams. Therefore 1 atom of silicon weighs (28/Avogardo's number) grams.
Do a search on Avogadro's number to find a more accurate value than I've used here; and search on atomic weight of silicon to find the value of 28.
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