Atoms contained in a human body

[corochena]

Given two people of different complexion, one short and chubby and the other one tall and thin, but same weight (180 lbs each):

a> Do they have the same number of atoms in their bodies

b> If not, will the percent difference be significant?

c>Is there a way to know an estimate of this number (number of atoms in a human body)?

 

[Drakkith]

There is no way to reliably figure this out without knowing the exact composition of every single cell in someones body. Just because 2 people weigh the same doesn't mean that they have the same number of atoms. One may have more carbon atoms than the other while the other may have more Hydrogen. I'd say just find an "average" amount for a person and use that.

 

[nasu]

You can estimate the order of magnitude of the average number of atoms.
If you want a better approximation, you can look up the average atomic composition of a human body and then estimate for each type of atom.

A table with the atomic composition is here
http://en.wikipedia.org/wiki/Composition_of_the_human_body
According to this table oxygen, carbon and nitrogen together make 86% of the body.
The atomic masses are 16, 12 and 14. Taking an "average" of 15 kg/kmol and a mass of 60 kg, the number of atoms will be

$$N= \frac{60}{15} N_{Avogadro}= 4 \cdot 6\times 10^{26}$$ atoms
or about $$10^{27}$$ atoms.

 

[alxm]

$$N= \frac{60}{15} N_{Avogadro}= 4 \cdot 6\times 10^{26}$$ atoms
or about $$10^{27}$$ atoms.

4 moles? You left out a factor x1000.

 

[nasu]

4 moles? You left out a factor x1000.

No, 4 kmoles. I used Avogadro's number in kmol^(-1)1 and the kilomoles/kg for average "molar mass".
I did not let out a factor of 1000.

Alternatively you can take the mass of person in grams and calculate in mols:

60,000/4 *6x10^23

which gives, of course, the same order of magnitude, 10^27.

Sorry I did not put explicitly all the units.

 

[uart]

I'd think that soft tissue would be mostly H, O, C and N atoms whereas bone would have more of the heavier elements like P and Ca. For this reason I'd say the the person with proportionately more soft tissue and less bone would have the largest number of atoms per kg. This I think would mean that the taller thinner person would have less atoms and the more portly person would have more atoms per kg.