2. New Way Chemistry for Hong Kong A-Level Book 11 Chapter 4 The Electronic Structure of Atoms 4.1The Electromagnetic Spectrum 4.2 Deduction of Electronic Structure from Ionization Enthalpies 4.3 The Wave-mechanical Model of the Atom 4.4 Atomic Orbitals

3. New Way Chemistry for Hong Kong A-Level Book 12 The Electronic Structure of Atoms Niels Bohr Bohr’s Model of H atom Chapter 4 The electronic structure of atoms (SB p.90)

4. New Way Chemistry for Hong Kong A-Level Book 13 The Electronic Structure of Atoms Niels Bohr Bohr’s Model of H atom Chapter 4 The electronic structure of atoms (SB p.90)

5. New Way Chemistry for Hong Kong A-Level Book 14 The Electromagnetic Spectrum 4.1 The Electromagnetic Spectrum (SB p.91)

6. New Way Chemistry for Hong Kong A-Level Book 15 Continuous spectrum of white light Fig.4-5(a) 4.1 The Electromagnetic Spectrum (SB p.92)

7. New Way Chemistry for Hong Kong A-Level Book 16 Line Spectrum of hydrogen 4.1 The Electromagnetic Spectrum (SB p.93) Fig.4-5(b)

8. New Way Chemistry for Hong Kong A-Level Book 17 The Emission Spectrum of Atomic Hydrogen UVVisible IR 4.1 The Electromagnetic Spectrum (SB p.93)

9. New Way Chemistry for Hong Kong A-Level Book 18 Interpretation of the Atomic Hydrogen Spectrum 4.1 The Electromagnetic Spectrum (SB p.94)

10. New Way Chemistry for Hong Kong A-Level Book 19 Interpretation of the Atomic Hydrogen Spectrum 4.1 The Electromagnetic Spectrum (SB p.94)

11. New Way Chemistry for Hong Kong A-Level Book 110 Interpretation of the Atomic Hydrogen Spectrum 4.1 The Electromagnetic Spectrum (SB p.94)

12. New Way Chemistry for Hong Kong A-Level Book 111 Bohr proposed for a hydrogen atom: 1. An electron in an atom can only exist in certain states characterized by definite energy levels (called quantum). 2. Different orbits have different energy levels. An orbit with higher energy is further away from the nucleus. 3.When an electron jumps from a higher energy level (of energy E 1 ) to a lower energy level (of energy E 2 ), the energy emitted is related to the frequency of light recorded in the emission spectrum by:  E = E 1 - E 2 = h 4.1 The Electromagnetic Spectrum (SB p.95)

13. New Way Chemistry for Hong Kong A-Level Book 112 4.1 The Electromagnetic Spectrum (SB p.96) How can we know the energy levels are getting closer and closer together?

14. New Way Chemistry for Hong Kong A-Level Book 113 4.1 The Electromagnetic Spectrum (SB p.97)  E = E 1 - E 2 = h Planck ’s constant Frequency of light emitted

15. New Way Chemistry for Hong Kong A-Level Book 114 Emission spectrum of hydrogen Absorption spectrum of hydrogen dark background (photographic plate) bright lines bright background (photographic plate) dark lines 4.1 The Electromagnetic Spectrum (SB p.97)

16. New Way Chemistry for Hong Kong A-Level Book 115 Production of the Absorption Spectrum Absorption spectrum of hydrogen 4.1 The Electromagnetic Spectrum (SB p.97) bright background (photographic plate) dark lines

17. New Way Chemistry for Hong Kong A-Level Book 116 Convergence Limits and Ionization What line in the H spectrum corresponds to this electron transition (n= ∞  n=1)? Last line in the Lyman Series For n=∞  n=1: 4.1 The Electromagnetic Spectrum (SB p.97) H (g) H + (g) + e -

18. New Way Chemistry for Hong Kong A-Level Book 117 The Uniqueness of Atomic Emission Spectra No two elements have identical atomic spectra  atomic spectra can be used to identify unknown elements. 4.1 The Electromagnetic Spectrum (SB p.99)

19. New Way Chemistry for Hong Kong A-Level Book 118 Ionization Enthalpy Ionization enthalpy (ionization energy) of an atom is the energy required to remove one mole of electrons from one mole of its gaseous atoms to form one mole of gaseous positive ions. The first ionization enthalpy M(g)  M + (g) + e -  H = 1st I.E. The second ionization enthalpy M + (g)  M 2+ (g) + e -  H = 2nd I.E. 4.2 Deduction of Electronic Structure from Ionization Enthalpies (p.100)

20. New Way Chemistry for Hong Kong A-Level Book 119 Evidence of Shells  shells 4.2 Deduction of Electronic Structure from Ionization Enthalpies (p.101)

21. New Way Chemistry for Hong Kong A-Level Book 120 Evidence of Sub-shells 4.2 Deduction of Electronic Structure from Ionization Enthalpies (p.102) 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8  subshells

22. New Way Chemistry for Hong Kong A-Level Book 121 Bohr’s Atomic Model and its Limitations Bohr considered the electron in the H atom (a one- electron system) moves around the nucleus in circular orbits. Basing on classical mechanics, Bohr calculated values of frequencies of light emitted for electron transitions between such ‘orbits’. The calculated values for the frequencies of light matched with the data in the emission spectrum of H. 4.3 The Wave-mechanical Model of the Atom (p.104)

23. New Way Chemistry for Hong Kong A-Level Book 122 Bohr’s Atomic Model and its Limitations Bohr tried to apply similar models to atoms of other elements (many-electron system), e.g. Na atom. Basing on classical mechanics, Bohr calculated values of frequencies of light emitted for electron transitions between such ‘orbits’. The calculated values for the frequencies of light did NOT match with the data in the emission spectra of the elements.  The electron orbits in atoms may NOT be simple circular path. 4.3 The Wave-mechanical Model of the Atom (p.104)

24. New Way Chemistry for Hong Kong A-Level Book 123 Wave Nature of Electrons A beam of electrons shows diffraction phenomenon  Electrons possess wave properties (as well as particle properties). 4.3 The Wave-mechanical Model of the Atom (p.104)

25. New Way Chemistry for Hong Kong A-Level Book 124 Wave Nature of Electrons Schrödinger used complex differential equations/wave fucntions to describe the wave nature of the electrons inside atoms (wave mechanic model). The solutions to the differential equations describes the orbitals of the electrons inside the concerned atom. An orbital is a region of space having a high probability of finding the electron. 4.3 The Wave-mechanical Model of the Atom (p.104)

26. New Way Chemistry for Hong Kong A-Level Book 125 Quantum Numbers Electrons in orbitals are specified with a set of numbers called Quantum Numbers: 1. Principal quantum number (n) n = 1, 2, 3, 4, …... 2. Subsidiary quantum number (l) l = 0, 1, 2, 3…, n-1 s p d f 3. Magnetic quantum number (m) m = -l, …, 0, …l 4. Spin quantum number (s) s= +½, -½ The solutions of the wave functions are the orbitals -- which are themselves equations describing the electrons. 4.3 The Wave-mechanical Model of the Atom (p.104)

27. New Way Chemistry for Hong Kong A-Level Book 126 4.3 The Wave-mechanical Model of the Atom (p.105) Principal quantum number (n) Subsidiary quantum number (l) Number of orbitals (2l+1) Symbol of orbitals Maximum number of electrons held 1011s1s2 20101 1313 2s2p2s2p 2626 3012012 135135 3s3p3d3s3p3d 5 6 10 401230123 13571357 4s4p4d4f4s4p4d4f 2 6 10 14 8 18 32

28. New Way Chemistry for Hong Kong A-Level Book 127 Each orbital can accommodate 2 electrons with opposite spin. 1s 2s 2p 3s 3p 3d 4s 4.3 The Wave-mechanical Model of the Atom (p.105)

29. New Way Chemistry for Hong Kong A-Level Book 128 The s Orbitals 4.4 Atomic Orbitals (p. 107)

30. New Way Chemistry for Hong Kong A-Level Book 129 The s Orbitals 4.4 Atomic Orbitals (p.107)

31. New Way Chemistry for Hong Kong A-Level Book 130 The p Orbitals 4.4 Atomic Orbitals (p.109)

32. New Way Chemistry for Hong Kong A-Level Book 131 The END