1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Mass of the nucleus

  1. May 28, 2017 #1
    1. The problem statement, all variables and given/known data
    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?

    2. Relevant equations
    fraction of mass = mass of nucleus/mass of atom

    3. 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...
     
  2. jcsd
  3. May 28, 2017 #2
    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.
     
  4. May 28, 2017 #3

    Borek

    User Avatar

    Staff: Mentor

    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.
     
  5. May 28, 2017 #4

    epenguin

    User Avatar
    Homework Helper
    Gold Member

    Where is this question from? I find it hard to believe that these masses are known to anything like 12 significant figures.
     
  6. May 29, 2017 #5

    Borek

    User Avatar

    Staff: Mentor

    9.10938356(11)×10−31 kg, if you copy digits only you will get even 13 sigfigs :wink:
     
  7. May 29, 2017 #6
    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.
     
  8. Jun 4, 2017 #7

    Borek

    User Avatar

    Staff: Mentor

    10-27 kg is not the mass of the proton nor any nucleus.
     
  9. Jun 9, 2017 #8
    Ah, my bad. I forgot the significant number behind the values..I got it now. Thanks!

    And also sorry for late reply ^^
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted