Not Bohr-ing Any More Quantum Mechanics & Electron Configurations

1. Not Bohr-ing Any MoreQuantum Mechanics & Electron Configurations Chapter 5

2. TEK • 6(E) express the arrangement of electrons in atoms through electron configurations and Lewis valence electron dot structures

3. Electron Models All Models agree: • Electrons move around the nucleus • There are energy levels that electrons must be in and NEVER in between (quanta) • Higher energy levels are farther from the nucleus

4. Quantum Mechanical Model There are energy levels, but they are not circular orbits. The energy levels have ELECTRON ORBITALS. These are like 3D clouds that represent where the electron might be found. Image from the Higher Education Academy Physical Sciences Centre

5. Electron Orbitals S orbitals Spherical 1 per energy level 2 electrons per sphere

6. Electron Orbitals P orbitals dumb bell shaped 3 per energy level 2 electrons per “dumb bell” www.geo.arizona.edu/xtal/geos306/fall07-2.htm

7. There are also d orbitals and f orbitals. They get complicated... SOURCE: www.geo.arizona.edu/xtal/geos306/fall07-2.htm

8. Electron Orbitals • The periods on the periodic table are the energy levels of the atom. • The higher the period number, the more elctrons the atom has and the higher the energy level of the valence electrons. • The periodic table is split up into regions, called blocks. • The block where an element “lives” indicates the type of orbital that contains its valence electrons.

9. Blocks of the Periodic Table s-block Representative Elements p-block Representative Elements d-block Transition Metals f-block Inner Transition Metals

10. Electron Configurations • Each atom has a unique ‘ground-state’ electron configuration. • The orbitals are too complicated to draw, so we use a special notation to plot where the electrons are in an atom. Each orbital is represented by a box. Electrons are represented by an up and a down arrow.  (means 2 electrons)

11. There are three 3 levels of organization… Energy Level = Row on the periodic table (1, 2, 3 ... 7) Energy levels are the first/biggest level of organization Sublevel = Periodic Table Block (s, p, d, f) Sub levels are second – energy levels contain sublevels Orbitals are third – sublevels contain orbitals Definition: an orbital is the space occupied by 2 (a pair of) electrons

12. An electron configuration for an atom is like a map, telling you where the electrons can be found. There are rules that govern why an electron will be in one sub-level rather than another.

13. S sub level S sub level has one orbital, so we draw one box. P sub level P sub level has 3 orbitals, so we draw 3 boxes.

14. D sub level D sub level has 5 orbitals, so we draw 5 boxes. F sub level F sub level has 7 orbitals, so we draw 7 boxes.

15. Electron Sub-Levels

16. Electron Sub-Levels

17. Period 1 – Energy Level 1 1 s orbital 2 e- Period 2 – Energy Level 2 1 s orbital 2 e- 3 p orbitals 6 e- Period 3 – Energy Level 3 1 s orbital 2 e- 3 p orbitals 6 e- Period 4 – Energy Level 4 1 s orbital 2 e- 3 p orbitals 6 e- 5 d orbitals 10 e- Period 5 – Energy Level 5 1 s orbital 2 e- 3 p orbitals 6 e- 5 d orbitals 10 e- Period 6– Energy Level 6 1 s orbital 2 e- 3 p orbitals 6 e- 5 d orbitals 10 e- 7 f orbitals 14 e- Period 7 – Energy Level 7 1 s orbital 2 e- 3 p orbitals 6 e- 5 d orbitals 10 e- 7 f orbitals 14 e- Electron Configurations Relate to the Levels in Bohr’s Model 2 8 8 18 18 32 32

18. Warm-Up: How do Electron orbitals relate to the Bohr Model? Period 1 – Energy Level 1 1 s orbital 2 e- Period 2 – Energy Level 2 1 s orbital 2 e- 3 p orbitals 6 e- Period 3 – Energy Level 3 1 s orbital 2 e- 3 p orbitals 6 e- Period 4 – Energy Level 4 1 s orbital 2 e- 3 p orbitals 6 e- 5 d orbitals 10 e- Period 5 – Energy Level 5 1 s orbital 2 e- 3 p orbitals 6 e- 5 d orbitals 10 e- Period 6– Energy Level 6 1 s orbital 2 e- 3 p orbitals 6 e- 5 d orbitals 10 e- 7 f orbitals 14 e- Period 7 – Energy Level 7 1 s orbital 2 e- 3 p orbitals 6 e- 5 d orbitals 10 e- 7 f orbitals 14 e- Total Electrons? Total Electrons?

19. Electron Configurations Rules for filling orbitals with electrons: • The Aufbau Principle • Build up from the lowest energy to the highest • The Pauli Exclusion Principle • The electrons in an orbital must be a “spin up” and “spin down” pair • Hund’s Rule • Electrons will occupy orbitals one by one before they pair up

20. Aufbau Principle – each electron must occupy the lowest energy orbital available in a sub level and energy level. Not all orbitals have the same energy. Energy: s  p  d  f energy increases 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p This chart shows the order that electrons fill sublevels. Although the D and F sublevels are on lower energy levels, they have high energy and do not fill until after the S and P for higher energy levels.

21. Pauli Exclusion Principle – 2 electrons may occupy one orbital but they must have opposite spin direction. This is why we draw electrons as arrows facing opposite directions. 

22. Hund’s Rule – Before 2 electrons will occupy the same orbital of a sub level, there must be at least one electron in every orbital of that sub level.   WRONG -This is not stable.     RIGHT -This is stable. Hund’s Rule paraphrased – do not double up electrons in an orbital (a box) until you have put one in each orbital for a sub level.

23. What element is this?  1s     2s 2p     3s 3p                4s 3d

24. Nickel  1s     2s 2p     3s 3p                4s 3d

25. The Periodic Table &Electron Configurations David's Whizzy Periodic Table

26. Valence Electrons • Electrons in the outermost energy level are called Valence Electrons • These are the electrons that form bonds

27. Written Electron Configurations • The electron configuration of an atom has a special form of notation. • It shows how the electrons are placed in the atomic orbital and energy levels. • The format consists of a series of numbers, letters and superscripts as shown below: 1s2 • The last numbers listed indicate the valence electrons…

28. Remember what I said about electron configurations being like a map? Let’s find some elements!

29. What element is this? • Determine what elements are denoted by the following electron configurations: • 1s22s22p63s23p4 ____________________ • 1s22s22p63s23p64s23d104p65s1__________ • [Kr] 5s24d105p3 ____________________ • [Xe] 6s24f145d6 ____________________ • [Rn] 7s25f11 ____________________

30. What element is this? • )1s22s22p63s23p4sulfur • )1s22s22p63s23p64s23d104p65s1rubidium • )[Kr] 5s24d105p3antimony • )[Xe] 6s24f145d6osmium • )[Rn] 7s25f11einsteinium

31. Valence Electrons • There must be an easier way of keeping track of these guys!

32. Electron Dot Structures • G.N. Lewis (1875-1946), an American chemist and university professor, devised and easy way to represent valence electrons. • Here are the rules: • Write the element symbol down • Find it’s group on the periodic table and decide how many valence electrons it has • Put a dot around the symbol for every electron • Start on the right…the next one goes on the left…then top…then bottom…lather, rise, repeat…

33. Example: Period 2 • Lithium Li Valence electrons: 1 • Li • Beryllium Be Valence electrons: 2 • Be • Boron B Valence electrons: 3 • B • Carbon C Valence electrons: 4 • C

34. You Try It!Period 2 • Nitrogen N Valence electrons: 5 • Oxygen O Valence electrons: 6 • Fluorine F Valence electrons: 7 • Neon Ne Valence electrons: 8

35. Period Lewis Dot Diagrams