2. V.Montgomery & R.Smith1 Atomic Structure From Indivisible to Quantum Mechanical Model of the Atom

3. V.Montgomery & R.Smith2 Quantum mechanical model(Modern Atomic Theory) Schr Ö dinger Heisenberg Pauli Hund

4. V.Montgomery & R.Smith3 Heisenberg’s Uncertainty Principle Impossible to determine both the position and the velocity of an e- in an atom simultaneously with great certainty.

5. V.Montgomery & R.Smith4 Schr Ö dinger e- not in neat orbits, but exist in regions called orbitals

6. V.Montgomery & R.Smith5 Orbital  region in space where the probability of finding an electron is the highest Definitions

7. V.Montgomery & R.Smith6 Quantum Numbers Definition: specify the properties of atomic orbitals and the properties of electrons in orbitals There are four quantum numbers

8. V.Montgomery & R.Smith7 Quantum Numbers (1) Principal Quantum Number, n

9. V.Montgomery & R.Smith8 Quantum Numbers Principal Quantum Number, n Values of n = 1,2,3,…  Positive integers only! Indicates the main energy level occupied by the electron

10. V.Montgomery & R.Smith9 Quantum Numbers Principal Quantum Number, n Values of n = 1,2,3,…  Describes the energy level, orbital size

11. V.Montgomery & R.Smith10 Quantum Numbers Principal Quantum Number, n Values of n = 1,2,3,…  Describes the energy level, orbital size As n increases, orbital size increases.

12. V.Montgomery & R.Smith11 Principle Quantum Number More than one e- can have the same n value These e- are said to be in the same e- shell The total number of orbitals that exist in a given shell = n 2

13. V.Montgomery & R.Smith12 Orbital Shapes For a specific main energy level, the number of sublevels possible is equal to n. Ex. n=2, can have two sublevels. A sublevel is assigned a letter: s, p, d, f, g, h

14. V.Montgomery & R.Smith13 Energy Level and Orbitals n=1, only s orbitals n=2, s and p orbitals n=3, s, p, and d orbitals n=4, s,p,d and f orbitals

15. V.Montgomery & R.Smith14 Atomic Orbitals Atomic Orbitals are designated by the principal quantum number followed by letter of their subshell Ex. 1s = s orbital in 1 st main energy level Ex. 4d = d sublevel in 4 th main energy level

16. The area where an electron can be found, the orbital, is defined mathematically, but we can see it as a specific shape in 3-dimensional space…

17. V.Montgomery & R.Smith16 Orbital Shapes s is spherical. One possible orientation.

18. x y z

19. The 3 axes represent 3-dimensional space x y z

20. For this presentation, the nucleus of the atom is at the center of the three axes. x y z

21. The 1s orbital is a sphere, centered around the nucleus

24. The 2s orbital is also a sphere.

25. The 2s electrons have a higher energy than the 1s electrons. Therefore, the 2s electrons are generally more distant from the nucleus, making the 2s orbital larger than the 1s orbital.

26. 1s orbital

27. 2s orbital

28. V.Montgomery & R.Smith27 Orbital Shapes p orbital. “dumbbell” shape

29. There are three p orbitals 3 possible orientations

30. The three 2p orbitals are oriented perpendicular to each other All three orbitals are identical of each other by energy, size and shape.The only difference is their orientation in space. DEGENERATE ORBITALS

31. This is one 2p orbital (2p y ) x y z

32. another 2p orbital (2p x ) x y z

33. the third 2p orbital (2p z ) x y z

34. The three 2p orbitals, 2p x, 2p y, 2p z x y z 3p, 4p, 5p, etc… have the same shape and number, just larger

35. V.Montgomery & R.Smith34 Orbital Shapes d orbital. “double dumbbell” or four-leaf clover It has 5 degenerate orbitals 5 possible orientations The 4d orbitals etc…are the same shape, only larger

36. V.Montgomery & R.Smith35 Orbital Shapes f orbital It has 7 degenerate orbitals 7 possible orientations

37. V.Montgomery & R.Smith36

38. V.Montgomery & R.Smith37 Energy Level and Orbitals n=1, only s sublevel n=2, s and p sublevels n=3, s, p, and d sublevels n=4, s,p,d and f sublevels

39. In the same energy level, energies of orbitals: s < p < d < f (because of the amount of repulsion between electrons) V.Montgomery & R.Smith38

40. V.Montgomery & R.Smith39 Quantum Numbers (4) Electron Spin Quantum Number, m s = + 1 / 2,  1 / 2 )

41. V.Montgomery & R.Smith40

42. Electron Spin QN 1. Relates to the spin states of the electrons. 2. Electrons are –1 charged and are spinning 3. The two possible spin directions are called +½ and –½

43. Like This Pauli Exclusion Principle No 2 e- in an atom can have the same set of four quantum numbers (n, l, m l, m s ). Therefore, no atomic orbital can contain more than 2 e-. and they must have opposite spin. No 2 e- in an atom can have the same set of four quantum numbers (n, l, m l, m s ). Therefore, no atomic orbital can contain more than 2 e-. and they must have opposite spin. Wolfgang Pauli 

44. Sublevels There are 4 sublevels(different shaped orbitals) s (has 1 orbital) p (has 3 orbitals) d (has 5 orbitals) f (has 7 orbitals) Each orbital can hold 2 electrons Can hold 2 e - Can hold 6 e - Can hold 10 e - Can hold 14 e -

45. Energy Level (n) Sublevels in Level # Orbitals in Sublevel Total # of Orbitals in Level 1s11 2s1 4 p3 3s19 p3 d5 4s116 p3 d5 f7

46. V.Montgomery & R.Smith45 Electron Configurations Electron Configurations: arrangement of e- in an atom There is a distinct electron configuration for each atom There are 3 rules for writing electron configurations:

47. V.Montgomery & R.Smith46 Aufbau Principle Aufbau Principle: an e- occupies the lowest energy orbital that can receive it.

48. V.Montgomery & R.Smith47

49. Aufbau order: V.Montgomery & R.Smith48 4s 3s 2s 1s 2p 3p 3d ENERGYENERGYENERGYENERGY

50. V.Montgomery & R.Smith49

51. 3p 4 Principal Energy Level Sublevel # of e - Writing Electron Configurations Describes e - location.

52. V.Montgomery & R.Smith51 Electron Configuration The total of the superscripts must equal the atomic number (number of electrons) of that atom.

53. V.Montgomery & R.Smith52 Orbital Diagrams These diagrams are based on the electron configuration. In orbital diagrams: Each orbital (the space in an atom that will hold a pair of electrons) is shown. The opposite spins of the electron pair is indicated.

54. V.Montgomery & R.Smith53 Orbital Diagram Rules 1. Represent each electron by an arrow 2. The direction of the arrow represents the electron spin 3. Draw an up arrow to show the first electron in each orbital. 4. Hund’s Rule(the principle of multiplicity): Distribute the electrons among the orbitals within sublevels so as to give the most unshared pairs. Put one electron in each orbital of a sublevel before the second electron appears.

55. Like This p orbitals Hund’s Rule One electron enters each orbital of equal energy (degenerate orbitals)until all the orbitals contain one electron with the same spin direction… …then they pair up.   Like This p orbitals      

56. V.Montgomery & R.Smith55 configuration1s2s2p x 2p y 2p z H1s 1 ↑ He1s 2 ↑ ↓ Li1s 2 2s 1 ↑ ↓↑ Be1s 2 2s 2 ↑ ↓ B1s 2 2s 2 2p 1 ↑ ↓ ↑ C1s 2 2s 2 2p 2 ↑ ↓ ↑↑ N1s 2 2s 2 2p 3 ↑ ↓ ↑↑↑ O1s 2 2s 2 2p 4 ↑ ↓ ↑↑ F1s 2 2s 2 2p 5 ↑ ↓ ↑ Ne1s 2 2s 2 2p 6 ↑ ↓

57. V.Montgomery & R.Smith56 Orbital Diagram Examples H  _ 1s Li   _ 1s 2s B    __ __ 1s 2s 2p N      _ 1s 2s 2p

58. Orbital filling table

59. We can use the previous Noble Gas as an abbreviation to indicate filled inner orbitals a. Na = 1s 2 2s 2 2p 6 3s 1 or [Ne]3s 1 b. Ca = [Ar]4s 2 c. Cl = [Ne]3s 2 3p 5 d. Rb = [Kr]5s 1 V.Montgomery & R.Smith58

60. V.Montgomery & R.Smith59 Dot Diagram of Valence Electrons When two atom collide, and a reaction takes place, only the outer electrons interact. These outer electrons are referred to as the valence electrons. Valence electrons are available to be lost, gained, or shared in the formation of chemical compounds

61. Lewis Dot(electron dot) diagrams A way of keeping track of valence electrons. Write the symbol. Put one dot for each valence electron Start at 3 o’clock move in a counterclockwise direction VideoVideo X

62. Distribute one valence electron at a time Do not pair (double up) any electrons until there is one electron in each of the four directions Pair up electrons once there is one in each of the four directions V.Montgomery & R.Smith61

63. The Lewis Dot diagram for Nitrogen l Nitrogen has 5 valence electrons. l First we write the symbol. N l Then add 1 electron at a time to each side. l Until they are forced to pair up.