多电子原子的核外电子排布 - 江南大学教务处

8.2 ARRANGEMENT OF EXTRANUCLEAR

ELECTRONS

多电子原子的核外电子排布

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8.2.1 Shielding effect and penetration effect 8.2.2 Orbital energy levels of multi-electron atom

8.2.3 Arrangement of extranuclear electrons

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1. Shielding effect

The shielding effect describes the decrease in attraction between an electron and the nucleus in any atom with more than one electron shell.

Effective nuclear charge

The effective nuclear charge is the net positive charge experienced by an electron in a multi-electron atom.

Shielding constant Z* = Z -σ

Nuclear charge

Values of shielding constant σ-Slater rules:

•An amount of 0.35from each other electron within the same group except for the [1s] group, where the other electron contributes only 0.30.

•If the group is of the [s p] type, an amount of0.85 from each electron with principal quantum number one less and an amount of 1.00 for each electron with an even smaller principal quantum number.

•If the group is of the [d] or [f], type, an amount of 1.00 for each electron with a smaller principal quantum number.

8.2.1 Shielding effect and penetration effect 2. Penetration effect

Penetration effect describes the behavior that electron enter into inner space of atom due to the attraction of nucleus.2s 与2p 轨道的径向分布图

The order of Penetration effect:

ns > np > nd > nf

休息

Pauling approximate energy level

Pauling approximate energy levels diagram:

>>>

>>

ns <np <nd <nf

8.2.2 Orbital energy levels of multi-electron atom 休息

Pauli Exclusion Principle

–

Each orbital can hold TWO electrons with opposite spins .

Wolfgang Pauli

1.Filling Rules for Electron Orbitals

Aufbau Principle

–

Electrons fill the lowest energy orbitals first.–

“Lazy Tenant Rule ”

2s

3s

4s

5s

6s

7s

1s

2p

3p

4p

5p

6p

3d

4d

5d

6d

4f

5f

1s

2s

2p 3s 3p 4s 4p 3d

4d

5s 5p 6s 7s 6p 6d 4f

5f 5d E n e r g y

Hund’s Rule

–Within a sublevel, place one electron

per orbital before pairing them.

–“Empty Bus Seat Rule”

2.Maximum Capacities of Subshells and Principal Shells

n 1 2 3 4...n

l 0 0 1 0 1 2 0 1 2 3

Subshell

designation s s p s p d s p d f

Orbitals in

subshell 1 1 3 1 3 5 1 3 5 7

Subshell

capacity 2 2 6 2 6 10 2 6 10 14

Principal shell

capacity 2 8 18 32 ...2n2

休息