Inner electron

As internal electron are electrons of the atom indicated that not the valence shell (outermost shell ) part and thus not chemical bonds are involved.

Inner electrons can be knocked out of the atom by particles with high kinetic energy . The electron that is now missing is replaced by an energetically higher electron. The energy released in the process can be given off as characteristic X-rays or as kinetic energy to an electron in the outer shell. The latter is then called the Auger electron and is used in Auger electron spectroscopy to examine solid bodies.