More generally, the nth ionization energy of an atom is the energy required to strip it of an nth electron after the first n - 1 have already been removed. The variation inside a period corresponds to the sublevels in the energy levels.įor H which has only a single electron moving around nucleus there will be a single value for the ionization potential.įor other elements, the removal of each subsequent electron requires even more energy, so a distinct and increasing value of ionization potential is measured for closer electrons of nucleus it becomes more difficult to remove additional electrons because they are closer to the nucleus and thus held more strongly by net positive charge of nucleus. Within each period there is an increasing energy value with some saw teeth. With each new period the ionization energy starts with a low value.
The periodic nature of ionization energy for the last electron of first 20 elements is presented in fig.
It is considered that s electrons are held closer to the nucleus, while f electrons are far from the nucleus and less tightly held. For instance, it takes less energy to remove a p electron than an s electron, even less energy to extract a d electron, and the least energy to extract an f electron. Ionization energies differ significantly, depending on the shell from which the electron is taken. Thus the ionization energy of the elements decreases as you go down the periodic table because it is easier to remove the electrons. With more energy levels, the outermost electrons (the valence electrons) are further from the nucleus and are not so strongly attracted to the nucleus. In the same column of periodic table, the effect of increased nuclear charge is balanced by the effect of increased shielding, and the number of energy levels becomes the predominant factor. Along periodic table it can be observed an increase of ionization energy with increasing nuclear charge. There is a dependence of ionization energy from nuclear charge, number of energy levels, and shielding.Īs the nuclear charge increases, the attraction between the nucleus and the electrons increases and it requires more energy to remove the outermost electron and that means there is higher ionization energy. Ionization energy exhibits a strong negative correlation with atomic radius. Generally speaking, ionization energies decrease down a group of the periodic table, and increase left-to-right across a period. The energy required to remove one electron from an isolated, gas-phase atom, when this atom is not hooked up to others like in a solid or a liquid, is called ionization energy (IE).
This is a revised material of a ionization energy variation presented in Atomic structure book.
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