1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Lesson Starter The electron configuration of carbon is 1s 2 2s 2 2p 2. An electron configuration describes the arrangement of electrons in an atom. The integers indicate the main energy level of each orbital occupied by electrons. The letters indicate the shape of the occupied orbitals. The superscripts identify the number of electrons in each sublevel. Chapter 4

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Homework: Chapter 4 review questions pg. 124-126 #1, 3-11, 13-41, (1-41 except #2 & 12) due by Tuesday.

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Objectives List the total number of electrons needed to fully occupy each main energy level. State the Aufbau principle, the Pauli exclusion principle, and Hund’s rule. Describe the electron configurations for the atoms of any element using orbital notation, electron- configuration notation, and, when appropriate, noble-gas notation. Chapter 4

4. End Show © Copyright Pearson Prentice Hall 4 Slide of 20 Electron Arrangement in Atoms If this rock were to tumble over, it would end up at a lower height. It would have less energy than before, but its position would be more stable. You will learn that energy and stability play an important role in determining how electrons are configured in an atom. 4.3

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Electron Configurations The arrangement of electrons in an atom is known as the atom’s electron configuration. The lowest-energy arrangement of the electrons for each element is called the element’s ground- state electron configuration. Chapter 4

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Electron Configuration Chapter 4 http://my.hrw.com/sh/hc6_003036809x/student/ch0 4/sec03/vc00/hc604_03_v00fs.htm

7. End Show © Copyright Pearson Prentice Hall 7 Electron Arrangement in Atoms > Slide of 20 Electron Configurations What are the three rules for writing the electron configurations of elements? 4.3

8. End Show Slide of 20 © Copyright Pearson Prentice Hall 8 Electron Arrangement in Atoms > Electron Configurations The ways in which electrons are arranged in various orbitals around the nuclei of atoms are called electron configurations. Three rules—the Aufbau principle, the Pauli exclusion principle, and Hund’s rule—tell you how to find the electron configurations of atoms. 4.3

9. End Show Slide of 20 © Copyright Pearson Prentice Hall 9 Electron Arrangement in Atoms > Electron Configurations Aufbau Principle According to the Aufbau principle, electrons occupy the orbitals of lowest energy first. In the Aufbau diagram below, each box represents an atomic orbital. 4.3

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Aufbau Principle Chapter 4 http://my.hrw.com/sh/hc6_003036809x/ student/ch04/sec03/vc01/hc604_03_v01 fs.htm

11. End Show Slide of 20 © Copyright Pearson Prentice Hall 11 Electron Arrangement in Atoms > Electron Configurations Pauli Exclusion Principle According to the Pauli exclusion principle, no two electrons in the same atom can have the same set of four quantum numbers. According to the Pauli exclusion principle, an atomic orbital may describe at most two electrons. To occupy the same orbital, two electrons must have opposite spins; that is, the electron spins must be paired. 4.3

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Relative Energies of Orbitals Section 3 Electron Configurations Chapter 4

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Pauli Exclusion Principle Chapter 4 http://my.hrw.com/sh/hc6_003036809x/student/c h04/sec03/vc02/hc604_03_v02fs.htm

14. End Show Slide of 20 © Copyright Pearson Prentice Hall 14 Electron Arrangement in Atoms > Electron Configurations Hund’s Rule According to Hund’s rule, orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron, and all electrons in singly occupied orbitals must have the same spin state. *just stated differently.. Hund’s rule states that electrons occupy orbitals of the same energy in a way that makes the number of electrons with the same spin direction as large as possible. 4.3

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Representing Electron Configurations Orbital Notation An unoccupied orbital is represented by a line, with the orbital’s name written underneath the line. An orbital containing one electron is represented as: Chapter 4

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Representing Electron Configurations, continued Orbital Notation An orbital containing two electrons is represented as: 1s1s He Chapter 4 The lines are labeled with the principal quantum number and sublevel letter. For example, the orbital notation for helium is written as follows:

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Orbital Notation Chapter 4 http://my.hrw.com/sh/hc6_003036809x/stude nt/ch04/sec03/vc03/hc604_03_v03fs.htm

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Representing Electron Configurations, continued Electron-Configuration Notation Electron-configuration notation eliminates the lines and arrows of orbital notation. Instead, the number of electrons in a sublevel is shown by adding a superscript to the sublevel designation. The helium configuration is represented by 1s 2. The superscript indicates that there are two electrons in helium’s 1s orbital. Chapter 4

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Reading Electron-Configuration Notation Chapter 4 http://my.hrw.com/sh/hc6_003036809x/st udent/ch04/sec03/vc04/hc604_03_v04fs.h tm

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Representing Electron Configurations, continued Sample Problem A The electron configuration of boron is 1s 2 2s 2 2p 1. How many electrons are present in an atom of boron? What is the atomic number for boron? Write the orbital notation for boron. Chapter 4

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Representing Electron Configurations, continued Sample Problem A Solution The number of electrons in a boron atom is equal to the sum of the superscripts in its electron- configuration notation: 2 + 2 + 1 = 5 electrons. The number of protons equals the number of electrons in a neutral atom. So we know that boron has 5 protons and thus has an atomic number of 5. To write the orbital notation, first draw the lines representing orbitals. 1s1s 2s2s 2p2p Chapter 4

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Representing Electron Configurations, continued Sample Problem A Solution, continued Next, add arrows showing the electron locations. The first two electrons occupy n = 1 energy level and fill the 1s orbital. 1s1s2s2s 2p2p Chapter 4

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Representing Electron Configurations, continued Sample Problem A Solution, continued The next three electrons occupy the n = 2 main energy level. Two of these occupy the lower- energy 2s orbital. The third occupies a higher- energy p orbital. 1s1s2s2s 2p2p Chapter 4

24. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Elements of the Second Period In the first-period elements, hydrogen and helium, electrons occupy the orbital of the first main energy level. According to the Aufbau principle, after the 1s orbital is filled, the next electron occupies the s sublevel in the second main energy level. Chapter 4

25. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Elements of the Second Period, continued The highest-occupied energy level is the electron- containing main energy level with the highest principal quantum number. Inner-shell electrons are electrons that are not in the highest-occupied energy level. Chapter 4

26. End Show Slide of 20 © Copyright Pearson Prentice Hall 26 Electron Arrangement in Atoms > Electron Configurations Orbital Filling Diagram 4.3

27. End Show © Copyright Pearson Prentice Hall 27 Slide of 26 Models of the Atom > Animation 5 Observe the characteristics of atomic orbitals. Atomic Orbitals Click here for animation ANIMATION TOOK A MINUTE TO LOAD. - This is a good animation for how the orbitals fill up.

28. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Writing Electron Configurations Section 3 Electron Configurations Chapter 4

29. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Elements of the Third Period After the outer octet is filled in neon, the next electron enters the s sublevel in the n = 3 main energy level. Noble-Gas Notation The Group 18 elements (helium, neon, argon, krypton, xenon, and radon) are called the noble gases. A noble-gas configuration refers to an outer main energy level occupied, in most cases, by eight electrons. Chapter 4

30. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Orbital Notation for Three Noble Gases Section 3 Electron Configurations Chapter 4

31. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Noble-Gas Notation Chapter 4 http://my.hrw.com/sh/hc6_003036809x/ student/ch04/sec03/vc05/hc604_03_v05 fs.htm

32. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Elements of the Fourth Period The period begins by filling the 4s orbital, the empty orbital of lowest energy. With the 4s sublevel filled, the 4p and 3d sublevels are the next available vacant orbitals. The 3d sublevel is lower in energy than the 4p sublevel. Therefore, the five 3d orbitals are next to be filled. Chapter 4

33. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Orbital Notation for Argon and Potassium Section 3 Electron Configurations Chapter 4

34. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Elements of the Fifth Period In the 18 elements of the fifth period, sublevels fill in a similar manner as in elements of the fourth period. Successive electrons are added first to the 5s orbital, then to the 4d orbitals, and finally to the 5p orbitals. Chapter 4

35. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Sample Problem B a. Write both the complete electron-configuration notation and the noble-gas notation for iron, Fe. b. How many electron-containing orbitals are in an atom of iron? How many of these orbitals are completely filled? How many unpaired electrons are there in an atom of iron? In which sublevel are the unpaired electrons located? Chapter 4

36. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Sample Problem B Solution a.The complete electron-configuration notation of iron is 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2. Iron’s noble-gas notation is [Ar]3d 6 4s 2. b.An iron atom has 15 orbitals that contain electrons. They consist of one 1s orbital, one 2s orbital, three 2p orbitals, one 3s orbital, three 3p orbitals, five 3d orbitals, and one 4s orbital. Eleven of these orbitals are filled, and there are four unpaired electrons. They are located in the 3d sublevel. The notation 3d 6 represents 3d Chapter 4

37. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Sample Problem C a.Write both the complete electron-configuration notation and the noble-gas notation for a rubidium atom. b.Identify the elements in the second, third, and fourth periods that have the same number of highest-energy-level electrons as rubidium. Chapter 4

38. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Electron Configurations Sample Problem C Solution a. 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 5s 1, [Kr]5s 1 b. Rubidium has one electron in its highest energy level (the fifth). The elements with the same outermost configuration are, in the second period, lithium, Li; in the third period, sodium, Na; and in the fourth period, potassium, K. Chapter 4

39. End Show © Copyright Pearson Prentice Hall 39 Slide of 20 Electron Arrangement in Atoms > Electron Configurations Simulation 2 Fill atomic orbitals to build the ground state of several atoms.

40. © Copyright Pearson Prentice Hall Slide of 20 End Show

41. © Copyright Pearson Prentice Hall Slide of 20 End Show

42. © Copyright Pearson Prentice Hall Slide of 20 End Show

43. © Copyright Pearson Prentice Hall Slide of 20 End Show Practice Problems for Conceptual Problem 1.1 Problem Solving 5.9 Solve Problem 9 with the help of an interactive guided tutorial.

44. End Show © Copyright Pearson Prentice Hall 44 Electron Arrangement in Atoms > Slide of 20 Exceptional Electron Configurations Why do actual electron configurations for some elements differ from those assigned using the aufbau principle? 4.3

45. End Show © Copyright Pearson Prentice Hall 45 Slide of 20 Electron Arrangement in Atoms > Exceptional Electron Configurations Some actual electron configurations differ from those assigned using the aufbau principle because half-filled sublevels are not as stable as filled sublevels, but they are more stable than other configurations.

46. End Show Slide of 20 © Copyright Pearson Prentice Hall 46 Electron Arrangement in Atoms > Exceptional Electron Configurations Exceptions to the aufbau principle are due to subtle electron-electron interactions in orbitals with very similar energies. Copper has an electron configuration that is an exception to the aufbau principle. 4.3

47. End Show © Copyright Pearson Prentice Hall Slide of 20 Section Quiz -or- Continue to: Launch: Assess students’ understanding of the concepts in Section 5.2 Section Quiz. 5.2.

48. © Copyright Pearson Prentice Hall Slide of 20 End Show 4.3 Section Quiz. 1.Identify the element that corresponds to the following electron configuration: 1s 2 2s 2 2p 5. a.F b.Cl c.Ne d.O

49. © Copyright Pearson Prentice Hall Slide of 20 End Show 4.3 Section Quiz. 2.Write the electron configuration for the atom N. a.1s 2 2s 2 2p 5 b.1s 2 2s 2 2p 3 c.1s 2 2s1p 2 d.1s 2 2s 2 2p 1

50. © Copyright Pearson Prentice Hall Slide of 20 End Show ` 3.The electron configurations for some elements differ from those predicted by the aufbau principle because the a.the lowest energy level is completely filled. b.none of the energy levels are completely filled. c.half-filled sublevels are less stable than filled energy levels. d.half-filled sublevels are more stable than some other arrangements. 4.3 Section Quiz.

51. © Copyright Pearson Prentice Hall Slide of 25 End Show Online Self-Check Quiz Complete the online Quiz and record answers. Ask if you have any questions about your answers. click here for online Quiz 4.3 (10 questions) You must be in the “Play mode” for the slideshow for hyperlink to work.

52. © Copyright Pearson Prentice Hall Slide of 27 End Show VIDEOS FOR ADDITIONAL INSTRUCTION Additional Videos for Section 4.3: Electron Configuration Electron Configuration (3:53)Electron Configuration Exceptions to Electron Configuration (2:58)Exceptions to Electron Configuration

53. © Copyright Pearson Prentice Hall Slide of 27 End Show SCI LINKS FOR CHAPTER Additional Student SCI LINKS for CHAPTER 4 The NSTA-sponsored SciLinks Web site contains links to accurate and up- to-date science information on the Internet. Just click on the button below to go to the SciLinks site at www.scilinks.orgwww.scilinks.org and log in. Then, type in the SciLinks code for the topic you want to research. The following is a list of the SciLinks codes for this chapter. Chapter 4: Arrangement of Electrons in Atoms Topic: Electromagnetic Spectrum SciLinks code: HC60482 Topic: Photoelectric Effect SciLinks code: HC61138 Topic: William Ramsay SciLinks code: HC61666