Why do you think it takes about half the energy to remove the first electron, compared to the energy needed to remove the last electron?
The two electrons in helium are NOT equivalent. The first ionization potential (energy required to remove the first electron) is #"24.6 eV"# and the second ionization potential (energy required to remove the second and last electron) is #"54.4 eV"# .
The second ionization potential agrees very well with what is predicted by the hydrogen-like atom model and the general Rydberg equation,
#DeltaE = Z^2 cdot R_H (1/n_i^2 - 1/n_f^2)#
Why do you think it takes about half the energy to remove the
first electron, compared to the energy needed to remove the last electron?
The two electrons in helium are NOT equivalent. The first ionization potential (energy required to remove the first electron) is
The second ionization potential agrees very well with what is predicted by the hydrogen-like atom model and the general Rydberg equation,
#DeltaE = Z^2 cdot R_H (1/n_i^2 - 1/n_f^2)#
Why do you think it takes about half the energy to remove the
first electron, compared to the energy needed to remove the last electron?
1 Answer
It has to overcome twice the attractive force of the proton on one electron.
Explanation:
Think about it as a balance of total energy, and magnetic forces.
First, the balance between the protons and the electrons means that pulling the first one away only needs to overcome the attractive force of effectively one proton.
The second one is held even more tightly, as the combined attraction of TWO protons is exerted on the ONE electron. That is also the reason that the numeric values are doubled. It may be easier to see that the force required to remove the second electron is doubled than to say that the force to remove the first one is half of the second.
