Energy level example sentences

In the preceding unit we have learnt that an electron in an atom is characterised by a set of four quantum numbers, and the principal quantum number (n ) defines the main energy level known as shell.Explain these trends in terms of nuclear charge and energy level.In this section we shall discuss the periodic trends in certain physical and chemical properties and try to explain them in terms of number of electrons and energy levels.This happens because the inner energy levels are filled with electrons, which serve to shield the outer electrons from the pull of the nucleus.