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Chemistry
Elements and Compounds

How many atoms are there on earth?

Answer

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July 21, 2008 4:56PM

The chemical composition of the Earth (by mass) is:

34.6% Iron

29.5% Oxygen

15.2% Silicon

12.7% Magnesium

2.4% Nickel

1.9% Sulfur

http://seds.lpl.arizona.edu/nineplanets/nineplanets/earth.html

The mass of the Earth is 5.97e24 kg = 5.97e27 g

Therefore the earth contains

2.07e27g Iron

1.76e27g Oxygen

9.1e26g Silicon

7.6e26g Magnesium

1.4e26g Nickel

1.1e26g Sulfur

The molar masses of these elements are:

55.9g Iron

16.0g Oxygen

28.1g Silicon

24.3g Magnesium

58.7g Nickel

32.1g Sulfur

Therefore the number of moles of each of these elements is:

3.7e25 Iron

1.10e26 Oxygen

3.2e25 Silicon

3.1e25 Magnesium

2e24 Nickel

3e24 Sulfur

for a total of 2.15e26 moles. Multiply by Avogadro's number to get number of atoms = 1.3e50 or so.

(what about the earth's atmoshere?)