Chapter 7. Atomic Structure and Periodicity. Copyright 2018 Cengage Learning. All Rights Reserved.

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1 Chapter 7 Atomic Structure and Periodicity

2 Chapter 7 Table of Contents (7.1) (7.2) Electromagnetic radiation The nature of matter (7.3) The atomic spectrum of hydrogen * (7.4) The Bohr model * (7.5) (7.6) (7.7) The quantum mechanical model of the atom * Quantum numbers Orbital shapes and energies (left out * can read on own but not on exam)

3 Chapter 7 Table of Contents (7.8) Electron spin and the Pauli principle (7.9) Polyelectronic atoms * (7.10) The history of the periodic table * (7.11) (7.12) (7.13) The Aufbau principle and the periodic table Periodic trends in atomic properties The properties of a group: The alkali metals

4 Section 7.1 Electromagnetic Radiation Electromagnetic Radiation One of the means by which energy travels through space Exhibits wavelike behavior Travels at the speed of light in a vacuum Copyright Cengage Learning. All rights reserved 4

5 Section 7.1 Electromagnetic Radiation Characteristics of Waves Wavelength (λ): Distance between two consecutive peaks or troughs in a wave Frequency (ν): Number of waves (cycles) per second that pass a given point in space Speed of light (c) = m/s Copyright Cengage Learning. All rights reserved 5

6 Section 7.1 Electromagnetic Radiation Relationship between Wavelength and Frequency Short-wavelength radiation has a higher frequency when compared to long-wavelength radiation This implies an inverse relationship between wavelength and frequency 1/ λ - Wavelength in meters Or ν - Frequency in cycles per second c - Speed of light ( m/s) = c

7 Section 7.1 Electromagnetic Radiation Figure The Nature of Waves

8 Section 7.1 Electromagnetic Radiation Figure Classification of Electromagnetic Radiation End class 8/17F at request of class did review of General Chemistry I so everyone starts on same page until 9/21 F

9 Section 7.1 Electromagnetic Radiation Here are the relationships between energy, wavelength and frequency. don t memorize c = c or = = = hc E h photon c = m/s h = J s speed of light Planck s constant Not going to ask you to do calculations with this but know the following: higher frequency( ) = lower wavelength( ) = higher energy(e)

10 Section 7.2 The Nature of Matter Figure Photoelectric Effect

11 Section 7.2 The Nature of Matter Dual Nature of Light Electromagnetic radiation exhibits wave and particulate properties

12 Section 7.5 The Quantum Mechanical Model of the Atom Figure Probability Distribution for the Hydrogen 1s Wave Function (Orbital) Probability distribution for the hydrogen 1s orbital in three-dimensional space Probability of finding the electron at points along a line drawn from the nucleus outward in any direction for the hydrogen 1s orbital

13 Section 7.6 Quantum Numbers Quantum Numbers Series of numbers that describe various properties of an orbital Principal quantum number (n) (period #) Angular momentum quantum number ( l ) (s,p,d,f block) Magnetic quantum number (m l ) (orbital) 13

14 Section 7.6 Quantum Numbers Principal Quantum Number (n) Has values (1, 2, 3,...) (period number) Gives size and energy of an orbital Larger n : The orbital becomes larger The electron spends more time away from the nucleus The energy increases since the electron is less tightly bound to the nucleus 14

15 Section 7.6 Quantum Numbers Angular Momentum Quantum Number (l ) (s,p,d,f block of periodic table) 0 to (n 1) for a given n Related to the shape of atomic orbitals Value of l for each orbital is assigned a letter Each set of orbitals with a given value of l (subshell) is designated by giving the value of n and the letter for l

16 Section 7.6 Quantum Numbers Magnetic Quantum Number (m l ) Has integral values between l, 0 l Value is related to the orientation of an orbital in space relative to the other orbitals in the atom Examples on doc camera 16

17 Section 7.6 Quantum Numbers Table Quantum Numbers for the First Four Levels of Orbitals in the Hydrogen Atom

18 Section 7.6 Quantum Numbers Interactive Example Electron Subshells For principal quantum level n = 5, determine the number of allowed subshells (different values of l ), and give the designation of each

19 Section 7.6 Quantum Numbers Interactive Example Solution For n = 5, the allowed values of l run from 0 to 4 (n 1 = 5 1) Thus, the subshells and their designations are as follows: l = 0 l = 1 l = 2 l = 3 l = 4 5s 5p 5d 5f 5g

20 Section 7.6 Quantum Numbers Exercise What are the possible values for the quantum numbers n, l, and m l? n = 1, 2, 3,... l l = 0, 1, 2,... (n 1) m l = l,..., 2, 1, 0, 1, 2,..., +l

21 Section 7.7 Orbital Shapes and Energies s Orbitals Characterized by their spherical shape Shape becomes larger as the value of n increases 2s and 3s orbitals have areas of high probability separated by areas of zero probability Number of nodes is given by n 1 don t know s orbital function is always positive in threedimensional space Copyright Cengage Learning. All rights reserved 21

22 Section 7.7 Orbital Shapes and Energies Figure 7.14 (b) - Representations of the Hydrogen 1s, 2s, and 3s Orbitals (looks spherical is enough to know) (node = areas of zero electron density) Slices of the three-dimensional electron density

23 Section 7.7 Orbital Shapes and Energies Figure 7.14 (c) - Representations of the Hydrogen 1s, 2s, and 3s Orbitals Surfaces that contain 90% of the total electron probability

24 Section 7.7 Orbital Shapes and Energies p Orbitals Have two lobes separated by a node at the nucleus, one lobe is positive & other lobe is negative Labeled according to the axis of the xyz coordinate system along which the lobes lie

25 Section 7.7 Orbital Shapes and Energies Figure Representation of the 2p orbitals Electron probability distribution for a 2p orbital Boundary surface representations of all three 2p orbitals

26 Section 7.7 Orbital Shapes and Energies d Orbitals Do not correspond to principal quantum levels n = 1 and n = 2 (no d for n=1 and 2, only for n = 3 & higher) (bc l =2 only possible for n=3 or higher) Have two different fundamental shapes d xz, d yz, d xy, and d 2 2 x y have four lobes centered in the plane indicated in the orbital label don t know d z 2 orbital has a unique shape with two lobes along the z axis and a belt centered in the xy plane

27 Section 7.7 Orbital Shapes and Energies Figure 7.17 (b) - The Boundary Surfaces of All Five 3d Orbitals, with the Signs (Phases) Indicated (don t need to know for Gen Chem)

28 Section 7.7 Orbital Shapes and Energies f Orbitals First occur in level n = 4 (don t need to know these shapes) Copyright Cengage Learning. All rights reserved 28

29 Section 7.8 Electron Spin and the Pauli Principle Electron Spin and the Pauli Exclusion Principle Electron spin quantum number (m s ) Can be +½ or ½, which implies that the electron can spin in one of two opposite directions end 9/21/18F Copyright Cengage Learning. All rights reserved 29

30 Section 7.8 Electron Spin and the Pauli Principle Pauli Exclusion Principle Pauli exclusion principle: In a given atom, no two electrons can have the same set of four quantum numbers An orbital can hold only two electrons, and they must have opposite spins

31 Section 7.8 Electron Spin and the Pauli Principle Figure The Spinning Electron

32 Section 7.11 The Aufbau Principle and the Periodic Table Aufbau Principle electrons added from bottom up As protons are added one by one to the nucleus to build up the elements, electrons are similarly added to hydrogen-like orbitals Represented in orbital diagrams where the arrow represents electrons spinning in a specific direction Example - Beryllium Be: 1s 2 2s 2 1s 2s 2p

33 Section 7.11 The Aufbau Principle and the Periodic Table Hund s Rule Lowest energy configuration for an atom is the one having the maximum number of unpaired electrons allowed by the Pauli principle in a particular set of degenerate orbitals Unpaired electrons have parallel spins Example C: 1s 2 2s 2 2p 2 1s 2s 2p

34 Section 7.11 The Aufbau Principle and the Periodic Table Valence Electrons Electrons present in the outermost principal quantum level of an atom Essential for bonding Core electrons: Inner electrons In the periodic table, the elements in the same group have the same valence electron configuration Elements with the same valence electron configuration exhibit similar chemical behavior Copyright Cengage Learning. All rights reserved 34

35 Section 7.11 The Aufbau Principle and the Periodic Table Figure Electron Configurations in the Type of Orbital Occupied Last for the First 18 Elements end class 9/24M

36 Section 7.11 The Aufbau Principle and the Periodic Table Electron Configuration of Transition Metals Configuration of transition metals is attained by adding electrons to the five 3d orbitals Scandium Sc: [Ar] 4s 2 3d 1 Titanium Ti: [Ar] 4s 2 3d 2 Vanadium V: [Ar] 4s 2 3d 3

37 Section 7.11 The Aufbau Principle and the Periodic Table Figure Valence Electron Configurations for Potassium through Krypton

38 Section 7.11 The Aufbau Principle and the Periodic Table Electron Configuration - Some Essential Points (periodic table on document camera) (n + 1)s orbitals always fill before the nd orbitals Lanthanide series: Group of 14 elements that appear after lanthanum Corresponds to the filling of the seven 4f orbitals Actinide series: Group of 14 elements that appear after actinium Corresponds to the filling of the seven 5f orbitals

39 Section 7.11 The Aufbau Principle and the Periodic Table Electron Configuration - Some Essential Points (continued) Labels for Groups 1A, 2A, 3A, 4A, 5A, 6A, 7A, and 8A indicate the total number of valence electrons for the atoms in these groups Main-group (representative) elements: Elements in groups labeled 1A, 2A, 3A, 4A, 5A, 6A, 7A, and 8A Members of these groups have the same valence electron configuration

40 Section 7.11 The Aufbau Principle and the Periodic Table Interactive Example Electron Configurations Give the electron configurations for sulfur (S), cadmium (Cd), using the periodic table inside the front cover of this book End 9/26/18 W

41 Section 7.11 The Aufbau Principle and the Periodic Table Interactive Example Solution Sulfur is element 16 and resides in Period 3, where the 3p orbitals are being filled Since sulfur is the fourth among the 3p elements, it must have four 3p electrons, and its configuration is: S: 1s 2 2s 2 2p 6 3s 2 3p 4 or [Ne]3s 2 3p 4

42 Section 7.11 The Aufbau Principle and the Periodic Table Interactive Example Solution (continued 1)

43 Section 7.11 The Aufbau Principle and the Periodic Table Interactive Example Solution (continued 2) Cadmium is element 48 and is located in Period 5 at the end of the 4d transition metals It is the tenth element in the series Has 10 electrons in the 4d orbitals in addition to the 2 electrons in the 5s orbital The configuration is: Cd: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 or [Kr]5s 2 4d 10 Give the electron configuration: examples on doc camera

44 Section 7.11 The Aufbau Principle and the Periodic Table Join In (12) try on own How many of the following electron configurations for the species in their ground state are correct? Ca: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 Mg: 1s 2 2s 2 2p 6 3s 1 V: [Ar]3s 2 3d 3 As: [Ar]4s 2 3d 10 4p 3 P: 1s 2 2s 2 2p 6 3p 5

45 Section 7.11 The Aufbau Principle and the Periodic Table Join In (12) (continued) a. 1 b. 2 end 9/28/18 F c. 3 d. 4 e. 5