Atomic Mass: Helium-4 Nucleus Contribution

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The discussion centers on calculating the fraction of a helium-4 atom's mass contributed by its nucleus. The mass of the helium-4 atom is given as 6.64648310224 g, with each electron's mass incorrectly noted, leading to confusion. Participants clarify that the mass of electrons should be expressed in scientific notation, emphasizing the importance of significant figures in calculations. The correct approach involves subtracting the total mass of electrons from the mass of the atom to find the nucleus's mass. Ultimately, the conversation highlights the need for accurate data and proper calculation methods in physics problems.
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Homework Statement


The mass of a helium-4 atom is 6.64648310224 g, and each of its two electrons has a mass of 9.10939310228 g. What fraction of this atom’s mass is contributed by its nucleus?

Homework Equations


fraction of mass = mass of nucleus/mass of atom

The Attempt at a Solution


I suppose I should calculate the mass of nucleus first. But I only have the mass of the electrons, no mass of neutron, also no density...
 
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Mass of nucleus = 6.64648310224
Mass of electrons = 9.10939310228 * 2
Mass of atom = 9.10939310228 * 2 + 6.64648310224 = 24.8652693068

Fraction of mass = mass of nucleus/mass of atom = 6.64648310224/24.8652693068 = 0.26729986392797124965341901615185

But the only problem is your data.
The masses of electron is not more than that of proton. And the mass of proton is too much.
I think you forgot to multiply the masses with power of 10s.
Well, this is the solution. Solve it in this way after you correct the data.
 
AryaUnderfoot said:
9.10939310228 g

That's incorrect on at least two accounts. First, digits after 9.1093 are wrong, second, the end should read not "28" but "e-28" - and this "e-" is what makes the most important difference.
 
Where is this question from? I find it hard to believe that these masses are known to anything like 12 significant figures.
 
epenguin said:
Where is this question from? I find it hard to believe that these masses are known to anything like 12 significant figures.

9.10938356(11)×10−31 kg, if you copy digits only you will get even 13 sigfigs :wink:
 
Aryamaan Thakur said:
Mass of nucleus = 6.64648310224
Mass of electrons = 9.10939310228 * 2
Mass of atom = 9.10939310228 * 2 + 6.64648310224 = 24.8652693068

Fraction of mass = mass of nucleus/mass of atom = 6.64648310224/24.8652693068 = 0.26729986392797124965341901615185

But the only problem is your data.
The masses of electron is not more than that of proton. And the mass of proton is too much.
I think you forgot to multiply the masses with power of 10s.
Well, this is the solution. Solve it in this way after you correct the data.
Ohh! I did a mistake
I thought 6.64648310224 is the mass of nucleus.

Correcting it!
Now,
Mass of nucleus = mass of atom - mass of electrons
And after you find it divide it with the mass of atom.

I hope you've verified the data.
 
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10-27 kg is not the mass of the proton nor any nucleus.
 
Aryamaan Thakur said:
Ohh! I did a mistake
I thought 6.64648310224 is the mass of nucleus.

Correcting it!
Now,
Mass of nucleus = mass of atom - mass of electrons
And after you find it divide it with the mass of atom.

I hope you've verified the data.
Ah, my bad. I forgot the significant number behind the values..I got it now. Thanks!

And also sorry for late reply ^^
 
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