Difference between comparing energies of a unielectronic species and a multi electronic species?
Answers
Isosters are those atoms which have similar number of electrons in their valence shell. For example F and Cl. They have 7 electrons each in their outermost shell. In fact every group in Mendeleev's period table represent the members of Isosters group. Isosters could be also from different groups. For example F- is isoster with H-.
Isoelectronic species are those atoms/ions having same electron numbers but with different nuclear charges.
In a single electron species only the principal quantum no.(n) is seen for comparing energy levels
Eg. in hydrogen 3s 3p 3d have equal energies. 4s has more energy than 3d
In multielectron species both principal and azimuthal quatum nos.(n+l) are seen
Eg. in carbon 3d has more energy than 4s as in 3d the enregy level is 3+2 = 5, in 4s the energy level is 4+0 = 4