Question #def40

1 Answer
Jan 9, 2017


If I am interpreting the question correctly, the answer is that the kinetic energy is +3.6 eV.


Here's the reason:

It can be shown (although the proof is lengthy, and I'm not certain you are asking to see it!), that for an electron in a bound state with a Coulomb potential acting, the potential energy is negative and has twice the absolute value of the kinetic energy.

Specifically, #V=-(1/(4pi epsilon_o)) 1/r#

while the kinetic energy is

#K=(1/(4pi epsilon_o)) 1/(2r)#

When you add these two quantities together, you get the total energy, which is

#E=-(1/(4pi epsilon_o)) 1/(2r)#

Note that the only difference in these last two expressions in the sign; the kinetic energy is necessarily positive, while the total energy is negative, indicating a bound state of electron within the atom.

So, the kinetic energy and the total energy have the same absolute value, but the total energy is -3.6 eV while the kinetic energy is +3.6 eV.