1. Chapter 2 - 1 CHAPTER 2: Atomic Structure and Bonding in Solids

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6. 6 Atomic Structure Valence electrons determine all of the following properties 1)Electrical 2)Thermal 3)Optical 4)Chemical

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8. 8 Electronic Structure Electrons have wavelike and particulate properties. –This means that electrons are in orbitals defined by a probability. –Each orbital at discrete energy level determined by quantum numbers. –Quantum # Designation n = principal (energy level-shell)K, L, M, N, O (1, 2, 3, etc.) l = subsidiary (orbitals)s, p, d, f (0, 1, 2, 3,…, n -1) m l = magnetic1, 3, 5, 7 (-l to +l) m s = spin½, -½

9. Chapter 2 - 9 Quantum Number 量子數 (Quantum Number) –1. 主量子數 (principal quantum number)(n) (1) 其值為大於或等於 1 的正整數 (2) 其物理意義為「可以決定能階之高低」， n 愈大，則 E n (n 值的能階 ) 愈高。 (3) 殼層 / 軌域 (shell) 的律定 n=1 層稱為 K 層， n=2 層稱為 L 層， n=3 層稱為 M 層， n=4 層稱為 N 層，如此類推 。

10. Chapter 2 - 10 Quantum Number 2. 角動量子數 (angular momentum number)( ℓ ) ℓ =0,1,2,3,…

11. Chapter 2 - 11 Quantum Number 3. 磁量子數 (magnetic number)(m 或 m ℓ ) m = 0, ±1, ±2, ±3, 4. 自旋量子數 (spin number)(S 或 m s ) 其值為 ±½

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13. Chapter 2 - 13 Electron Energy States 1s1s 2s2s 2p2p K-shell n = 1 L-shell n = 2 3s3s 3p3p M-shell n = 3 3d3d 4s4s 4p4p 4d4d Energy N-shell n = 4 have discrete energy states tend to occupy lowest available energy state. Electrons... Adapted from Fig. 2.4, Callister 7e.

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15. Chapter 2 - 15 Why? Valence (outer) shell usually not filled completely. Most elements: Electron configuration not stable. SURVEY OF ELEMENTS Electron configuration (stable)... 1s1s 2 2s2s 2 2p2p 6 3s3s 2 3p3p 6 (stable)... 1s1s 2 2s2s 2 2p2p 6 3s3s 2 3p3p 6 3d3d 10 4s4s 2 4p4p 6 (stable) Atomic # 18... 36 Element 1s1s 1 1Hydrogen 1s1s 2 2Helium 1s1s 2 2s2s 1 3Lithium 1s1s 2 2s2s 2 4Beryllium 1s1s 2 2s2s 2 2p2p 1 5Boron 1s1s 2 2s2s 2 2p2p 2 6Carbon... 1s1s 2 2s2s 2 2p2p 6 (stable) 10Neon 1s1s 2 2s2s 2 2p2p 6 3s3s 1 11Sodium 1s1s 2 2s2s 2 2p2p 6 3s3s 2 12Magnesium 1s1s 2 2s2s 2 2p2p 6 3s3s 2 3p3p 1 13Aluminum... Argon... Krypton Adapted from Table 2.2, Callister 7e.

16. Chapter 2 - 16 Electron Configurations Valence electrons – those in unfilled shells Filled shells more stable Valence electrons are most available for bonding and tend to control the chemical properties –example: C (atomic number = 6) 1s 2 2s 2 2p 2 valence electrons

17. Chapter 2 - 17 Electronic Configurations ex: Fe - atomic # = 26 valence electrons Adapted from Fig. 2.4, Callister 7e. 1s1s 2s2s 2p2p K-shell n = 1 L-shell n = 2 3s3s 3p3p M-shell n = 3 3d3d 4s4s 4p4p 4d4d Energy N-shell n = 4 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2

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19. Chapter 2 - 19 The Periodic Table Columns: Similar Valence Structure Adapted from Fig. 2.6, Callister 7e. Electropositive elements: Readily give up electrons to become + ions. Electronegative elements: Readily acquire electrons to become - ions. give up 1e give up 2e give up 3e inert gases accept 1eaccept 2e O Se Te PoAt I Br He Ne Ar Kr Xe Rn F ClS LiBe H NaMg BaCs RaFr CaKSc SrRbY

20. Chapter 2 - 20 Ranges from 0.7 to 4.0, Smaller electronegativityLarger electronegativity Large values: tendency to acquire electrons. Adapted from Fig. 2.7, Callister 7e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by Cornell University. Electronegativity

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24. Chapter 2 - 24 Predominant bonding in Ceramics Adapted from Fig. 2.7, Callister 7e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 by Cornell University. Examples: Ionic Bonding Give up electronsAcquire electrons NaCl MgO CaF 2 CsCl

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26. Chapter 2 - 26 C: has 4 valence e -, needs 4 more H: has 1 valence e -, needs 1 more Electronegativities are comparable. Adapted from Fig. 2.10, Callister 7e. Covalent Bonding similar electronegativity  share electrons bonds determined by valence – s & p orbitals dominate bonding Example: CH 4 shared electrons from carbon atom shared electrons from hydrogen atoms H H H H C CH 4

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34. Chapter 2 - 34 Arises from interaction between dipoles Permanent dipoles-molecule induced Fluctuating dipoles -general case: -ex: liquid HCl -ex: polymer Adapted from Fig. 2.13, Callister 7e. Adapted from Fig. 2.14, Callister 7e. SECONDARY BONDING asymmetric electron clouds +-+- secondary bonding HHHH H 2 H 2 secondary bonding ex: liquid H 2 H Cl H secondary bonding secondary bonding +-+- secondary bonding

35. Chapter 2 - 35 Bond length, r Bond energy, E o Melting Temperature, T m T m is larger if E o is larger. Properties From Bonding: T m r o r Energy r larger T m smaller T m EoEo = “bond energy” Energy r o r unstretched length

36. Chapter 2 - 36 Coefficient of thermal expansion,   ~ symmetry at r o  is larger if E o is smaller. Properties From Bonding :  =  (T 2 -T 1 )  L L o coeff. thermal expansion  L length,L o unheated, T 1 heated, T 2 r o r smaller  larger  Energy unstretched length EoEo EoEo

37. Chapter 2 - 37 Type Ionic Covalent Metallic Secondary Bond Energy Large! Variable large-Diamond small-Bismuth Variable large-Tungsten small-Mercury smallest Comments Nondirectional (ceramics) Directional (semiconductors, ceramics polymer chains) Nondirectional (metals) Directional inter-chain (polymer) inter-molecular Summary: Bonding

38. Chapter 2 - 38 Ceramics (Ionic & covalent bonding): Metals (Metallic bonding): Polymers (Covalent & Secondary): Large bond energy (E o ) large T m (melting point) large E (= dF / dr) ro, (stiffness, modulus of elasticity) small  Variable bond energy moderate T m moderate E moderate  Directional Properties Secondary bonding dominates small T m small E large  Summary: Primary Bonds secondary bonding

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