Why are the sublevels within a principal level split into different energies for multi-electron atoms but not for hydrogen atom?

Kindly check the explanation section.

Explanation:

Hydrogen in the periodic chart/table is the first element on the periodic table with binding energy of 0.000± 0.0000 keV, Isotopic mass of 1.007825 u, one or single proton and a spin value of half(1/2).

The first thing to note for the fact that hydrogen's sublevels within a principal level does not split into seperate or different energies is that THERE IS A VACANT GROUND STATE IN HYDROGEN ATOM. With this, it makes it impossible for the electrons that are inside to get infiltrated which is the case with the atoms with multielectron.

NB: Penetration is done by electrons outside.

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

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