Nuclear Physics - Mass Defect & Binding Energy

[Kylah]

[SOLVED] Nuclear Physics - Mass Defect & Binding Energy

1. Carbon 12 ($$^{12}_{6}$$C) has a nuclear mass of 1.99264 x 10^-26 kg, a proton has a mass of 1.67353 x 10^-27, and a neutron has a mass of 1.67492 x 10^-27 kg. Calculate the mass defect for carbon 12.

My equation looks like this:
$$\Delta$$m = [Z(m_p+m_e) + (A-Z)m_n]-m_atom

Where:
$$\Delta$$m = ?
m_p = 1.67353 x 10^-27 kg
m_n = 1.67353 x 10^-27 kg
m_e =
m_atom = 1.99264 x 10^-26
Z = 6
A = 12


What I'm not sure is what m_e is. Could anybody help me?

 

[Vuldoraq]

Hey,

The mass of an electron is 1836 times smaller than the mass of a proton $$m_{e}=9.10938*10^{-31}Kg$$, though I think that even if you take it into consideration in your calculation you will find it makes no difference to your result, since your other numbers don't have sufficient decimal places.

 

[Chi Meson]

Actually the electron mass will be significant here. 12 electrons will have a total mass of 0.01093 x 10^-27kg. With 6 significant digits, this mass can not be ignored.

 

[Kylah]

Actually the electron mass will be significant here. 12 electrons will have a total mass of 0.01093 x 10^-27kg. With 6 significant digits, this mass can not be ignored.

Thank you!