More the gap, more the energy
So the electron falling from Third shell will release more energy.
If an electron is in the second principle energy level, that is, n = 2, then that electron could be in an s or p orbital.
It would release energy. It had to absorb it in order to get from 2 to 3. Law of conservation of energy says it must now release it to fall back.
The first element with an electron in the second energy level is lithium. Lithium has three electrons, with two in the first energy level and one in the second energy level.
Electrons are attracted to the nucleus of the atom of which they are a part; this is because of the electrostatic force between the negatively charged electron and the positively charged nucleus. Therefore it takes energy in order to pull an electron farther away from the nucleus and to enable it to remain at a greater distance. This is exactly the same phenomenon as raising a heavy object such as, let us say, a bowling ball, to a greater elevation. It takes energy to do it, since you have to overcome the force of gravity.
hydrogen has only one electron so after you remove that electron you do not have any electrons left to remove so hydrogen doesn't have a 2nd ionization energy. hydrogen has 1 proton and 1 electron.
The energy to remove 1 electron is the first ionization energy. To remove a second electron requires more energy. This is because the electron being removed now has to overcome the +1 positive charge introduced after the 1st electron was removed.
Selenium does not have a second electron affinity because adding an additional electron to selenium would require more energy to overcome the repulsion between the negatively charged electron and the negatively charged selenium ion. In other words, the energy required to add a second electron to selenium is higher than the energy released in the process.
Chlorine has a negative second electron affinity because it releases energy when gaining an additional electron. This makes it less likely to accept a second electron compared to its first electron affinity, which is positive.
First ionization energy is the energy required to remove the first outermost electron from an atom. The second ionization energy is the energy required to remove the next available electron, and is greater than the first IE. The third IE is that energy needed to remove the third electron, and is greater the the second IE.
The second level is associated with higher energy than the first is. Keep increasing the energy of an electron enough, and eventually it breaks free of the atom completely.
The second ionization energy for lithium is greater than the first because removing the second electron requires breaking a stronger bond due to the higher effective nuclear charge after the first electron is removed. This leads to a greater energy input to remove the second electron compared to the first.
To create an electron affinity reactor you will have to use the second ionization energy.