Where this energy to excited electron comes from?

The energy required to excite the electron from ground state of hydrogen atom to first excited state is

If radiation correcsponding to second line of “Balmer series” of Li^(2+) ion, knocked out electron from first excited state of H-atom, then kinetic energy of ejected electron would be:

Does the electron retain the energy at excited state forever ?

The energy required to emit an electron from the surface of a metal is called

The total energy of an electron in the first excited state of hydrogen atom is -3.4eV. What is the kinetic energy of the electron in this state ?

In a hydrogen atom, if energy of an electron in ground state is 13.6eV, then the energy in the nearest excited state is

In a hydrogen atom, if energy of an electron in ground state is 13.6 eV, then the energy in the 2nd excited state is

The energy of the ground electronic state of hydrogen atom is -13.6e V. The energy of the first excited state will be :

The total energy of an electron in the first excited state of the hydrogen atom is about -3.4 eV. What is the kinetic energy of the electron in this state ?