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4.
Cotton Atomic Orbital Energy Level Diagram
Cotton (Cotton) believes that the order of the energy levels of the atomic orbitals of different elements is different, and not all the atomic orbitals of the elements have energy level staggered phenomena (Figure 5-12)
.
Figure 5-11 Approximate energy level diagram of atomic orbitals
The energy level diagram of Cotton's atomic orbital reflects the relationship between the energy of the orbital and the atomic number.
As the atomic number increases, the energy of all orbitals decreases, but the magnitude of the decrease is different, resulting in energy level splitting; the value of the angular quantum number l is small The drop rate of is large, resulting in energy level interleaving
It can be seen from Figure 5-12 that the orbital energy levels of elements 1-14 do not interleave, E 4s > E 3d ; the orbital energy levels of element 15-20 interleave, E 4s <E 3d ; after 21, the 4s and 3d orbitals of the elements The energy levels are not interleaved, E 4s > E 3d
.
Figure 5-12 Energy level diagram of Cotton's atomic orbital (partial)
The Korton atomic orbital energy level diagram is suitable for judging the energy level of the orbital filled with electrons.
It can explain the sequence of elements losing electrons, that is, the electrons of the orbital with a large principal quantum number are lost first.
The energy level of the approximate energy level diagram of Pauling's atomic orbit is the energy in the empty orbit, which is suitable for the arrangement of electrons in the orbit, but it cannot explain the order in which the elements lose electrons
.
5.
Slater Rules
The Slater rule provides a method to calculate the shielding constant σ semi-quantitatively, and then calculate the energy of the orbital and electrons, namely
The Slater rule groups the tracks into
(1s)(2s 2p)(3s 3p)(3d)(4s 4p)(4d)(4f).
.
The calculation principles of shielding constant σ are as follows:
(1) The outer layer of electrons has no shielding of the inner layer of electrons, that is, the shielding constant σ=0 of the right orbital electrons against the left orbital electrons
.
(2) The shielding constant σ=0.
30 between two electrons in the 1s orbit, and the shielding constant σ=0.
35 between other electrons in the same group
.
(3) When discussing the shielding of electrons in the (ns np) group of orbitals, the shielding constant of each electron on the (n-1) orbital layer is 0.
85; each of the orbitals in the (n-2) layer and the inner layer The shielding constant of electrons σ=1.
00
.
(4) When discussing the shielding of the orbital electrons in the (nd) or (nf) group, the shielding constant of all the orbital electrons in the left group is σ=1.
00
.
[Example 5-2] Use Slater's rule to calculate the energy levels of the 4s and 3d orbital electrons of Ni
.
The electron arrangement formula for solving Ni is 1S 2 2S 2 2p 6 3S 2 3p 6 3d 8 4S 2 , according to Slater’s rule, the shielding constant of 4s electrons is
σ4s=0.
35+0.
85×16+1.
00×10=23.
95
The energy of Ni's 4s electron is
The shielding constant of Ni 3d electrons is
σ 3d =0.
35×7+1×18=20.
The energy of the 3d electron of Ni is
The calculation results show that the energy of Ni 3d orbital electrons is lower than that of 4s orbital electrons
Related links: Energy levels of multi-electron atomic orbitals (1)