Write the electron configuration of the atom in the third row of the periodic table that has the smallest ei4.

                 Silicon = Si =  1s², 2s², 2p⁶, 3s², 3p²

                         Ionization Energy (Ei) is the minimum amount of energy required to remove the valence electron from the valence shell of an atom in its gaseous state. Ionization Energies are further classified as,

                                      Ei₁  =  First Ionization Energy

                                     Ei₂  =  Second Ionization Energy

                                     Ei₃  =  Third Ionization Energy

                                     Ei₄  =  Fourth Ionization Energy

And so on

First ionization energy is the energy required to remove electron from neutral atom. Second ionization energy is the energy required to remove electron from M⁺ ion. Third ionization energy is the energy required to remove electron from M⁺² and so on

Ei₄ in case of Si means the removal of electron from Si⁺³. As after the removal of fourth electron Si gains a noble gas configuration of Neon that is why it has the least fourth ionization energy.