r2R2 Shielding 1s 4f 4d494s Penetration: 4s>4p>4d>4f r A 4s electron penetrates the 1s orbital better than a 4p electron IV-11
Shielding A 4s electron penetrates the 1s orbital better than a 4p electron r2R2 r Penetration: 4s > 4p > 4d > 4f 1s 4f 4d 4s 4p IV-11
Another View of 2s vs 2p Shielding 1s 2s 1s 2p shielded electron density 2s Penetrates More into 1s Than Does 2p 2s is Therefore Lower in E Than 2p V-12
Another View of 2s vs 2p Shielding 1s 2p shielded electron density 2s 1s 2s Penetrates More into 1s Than Does 2p 2s is Therefore Lower in E Than 2p IV-12
Energy of Multi-Electron Atoms 0 (e t c.) 4p 3d 3p E 23 2p due to shielding,orbitals with the same principal quantum number(n)do NOT have the same energies 1s IV-13
1s 2s 2p 3s 3p 5s 4p 3d Energy of Multi-Electron Atoms 4s E (e t c.) 0 due to shielding, orbitals with the same principal quantum number(n) do NOT have the same energies IV-13
Mnemonic for Filling Order hence the filling order is: 1S,2s,2p,3S, 2s 2p 3p,4s,3d,etc. 3 3 3d 4p 4d 4f 5 50 5d 5f IV-14
1s 2s 3s 4s 5s 2p 3p 4p 5p 3d 4d 5d 4f 5f Mnemonic for Filling Order hence the filling order is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, etc. IV-14
Valence Electrons 5s element 4s 3d shell electrons in shell 3p valence electrons 3s 1.H(1s)1 (underlined) 2.He(1s)2 2p 2s 3.Li(1s)2(2s)1 2p-orbital 4.Be(1s)2(2s)2 5.B(1s)22s)2(2p)1 1s 6.C(1s)22s)(2p)2 Valence Electrons: 7.N(1s)22s)2(2p)3 electrons in the outermost 8.0(1s)2(2s)2(2p)4 shell (in other words,the set 9.F(1s)2(2s)2(2p)5 个个个110 T1110 of electrons with highest 10.Ne(1s)2(2s)2(2p)6 principal quantum number) ·etc. V-15
1s 2s 2p 3s 3p 5s 4p 3d 4s E 1. H (1s)1 2. He (1s)2 3. Li (1s)2(2s)1 4. Be (1s)2(2s)2 e t c. 0 5. B (1s)2(2s)2(2p)1 6. C (1s)2(2s)2(2p)2 7. N (1s)2(2s)2(2p)3 8. O (1s)2(2s)2(2p)4 9. F (1s)2(2s)2(2p)5 10. Ne (1s)2(2s)2(2p)6 element shell electrons in shell valence electrons (underlined) 2p- orbital e t c. Valence Electrons Valence Electrons: electrons in the outermost shell (in other words, the set of electrons with highest principal quantum number) ↑ ↑ ↑ ↑ ↑ ↑ ↑↓ ↑ ↑ ↑↓ ↑↓ ↑ ↑↓ ↑↓ ↑↓ IV-15