2. Chapter 7 Development of a New Atomic Model The Quantum Model of the Atom Electron Configuration Periodicity

3. I. Development of a New Atomic Model A. Light behaves as both a wave and a particle B. The wave attributes of light include: 1) wavelength -  (lamda)  the distance from wave to wave (nm) 2) frequency -   nu   number of waves per second (s -1 ; Hz) 3)   c * c = 3.00 x 10 8 m/sec watch the units!!!

4. C. Electromagnetic Spectrum 1) this is the range of all wavelengths/frequencies and what they are called 2) the smaller the wavelength, the more energy it has Worksheet Problems: # 1,2 D. The particle nature of light - photoelectric effect 1) electromagnetic radiation is emitted in specific ‘packages’ of energy, called photons 2) this radiation does not get to be emitted until the electrons have obtained a predetermined amount of minimum energy, called a quantum. * analogy: a quarter-only coin operated vending machine

5. 3) The energy associated with a specific wavelength or frequency is: E = hc E = h  * wavelength must be in METERS…. frequency in Hz * units for Energy are Joules Worksheet Problem - # 3 h = 6.636 x 10 -34 Js c = 3.00 x 10 8 m/s

6. E. Hydrogen atom line emission spectrum 1) ground state - the lowest energy state of an e- 2) excited state - higher energy state than ground state 3) the electron in hydrogen are able to be promoted to higher energy levels when given a current 4) the color of light given off is made up wavelengths of energy from the electron giving off the energy it absorbed 5) the energy released = E 2 - E 1 6) the resulting spectrum is called a LINE EMISSION SPECTRUM 7) The Energy released can be calculated once the wavelength of the emitted photon is known:

7. ex: To calculate the wavelength of emission by the photon: 1 = 1.09687 x 10 5 cm -1 1 n1n1 2 1 n2n2 2 - lower energy level higher energy level worksheet problem - # 4

8. II. Quantum Numbers A. Any mathematical expression with X and Y variables can be graphed to show the relationships between them. B. An expression with X,Y and Z variables will result in a 3-D graph….. C. A mathematical equation was used to indicate the probable location of each electron in an atom 1) the variables are called QUANTUM NUMBERS 2) each quantum number is restricted to allow only certain values 3) the mathematical results are numerical answers, but can also be shown graphically (3-D)

9. D. These are the 4 quantum numbers, meaning and allowed values: symbol stands for... allowed values comments nenergy leveln = 1,2,3...no zero; no - l shape of 3-D region l = 0,1,2,3… (n-1) these letters are assigned to each value... s,p,d,f m orientation of shape m = - l… 0… + l ex: if l = 1, then m = -1, 0, +1 sspin of e- s = + 1/2, - 1/2 e- spin is either clockwise or counter clockwise ex: if n = 1, what l,m and s are allowed? l = 0 (only) m = 0 (only)… or ‘s’ shape s = +1/2 OR - 1/2

10. ex: Which, if any, of these sets of 4 q.n. has an error? Fix it. nlms 201+1/2 since l = 0, only m = 0 is allowed 220+1/2 since n=2, l can = 0 or 1… not 2! 431-1/2 no errors 000+1/2 n cannot = 0 worksheet problems # 7,8,9 Q: What energy level and shape is indicated by n=2, l = 0? A: 2s Q: What about n = 4, l = 3? A: 4d

11. D. These are the 4 quantum numbers, meaning and allowed values: symbol stands for... allowed values comments nenergy leveln = 1,2,3...no zero; no - l shape of 3-D region l = 0,1,2,3… (n-1) these letters are assigned to each value... s,p,d,f m orientation of shape m = - l… 0… + l ex: if l = 1, then m = -1, 0, +1 sspin of e- s = + 1/2, - 1/2 e- spin is either clockwise or counter clockwise

12. III. Electron Configuration A. Each electron is assigned an address to indicate its location in the atom B. Each ORIENTATION value is allowed 2 electrons: ex: if l = 1, then m = -1, 0, +1 symbol stands for... allowed values comments nenergy leveln = 1,2,3...no zero; no - l shape of 3-D region l = 0,1,2,3… (n-1) these letters are assigned to each value... s,p,d,f m orientation of shape m = - l… 0… + l sspin of e- s = + 1/2, - 1/2 e- spin is either clockwise or counter clockwise l = 1 means the ‘p’ shape region m = -1 (which can have 2 e-)…. = 0 (which can have 2 e-)…. = +1 (which can have 2 e-)…. therefore, ‘p’ can have 6 e- how many can s, d, and f have? s = 2… d = 10… f = 14

13. C. So, this is the limit of e- each region can have: s = 2e-…. p = 6e-… d = 10e- … f = 14e- D. The first 3 energy levels are limited in having only some of the shapes: n = 1….. l = 0 (s shape) n = 2….. l = 0 (s shape) l = 1 (p shape) n = 3….. l = 0 (s shape) l = 1 ( p shape) l = 2 (d shape) E. The energy levels fill up in numerical order to start (I.e. all the 1st level, all the 2nd level)….. ex: 1s 2 2s 2 2p 6

14. Example 1: Write the electron configuration for these elements: H =1 1 s energy level shape # e- He =1s 2 Li =1s 2 2s 1 C = 1s 2 2s 2 2p 2 B =1s 2 2s 2 2p 1

15. G. How can you determine the order to follow? 1s 2s 3s 4s 5s 6s 7s 2p 3p 4p 5p 6p 7p 3d 4d 5d 6d 7d 4f 5f 6f 7f This chart is used by following the boxes diagonally from r-l. F… but then the order depends on energy hierarchies (I.e. its easier to fill some of the 4th before finishing the 3rd)

16. ex: Write the electron configuration for Calcium Ca = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 H. Miscellaneous topics 1) noble gas shortcut - write the previous noble gas (group 18) symbol in square brackets, then continue from there. ex: Ca = [Ar] 4s 2 2) arrow notation - each orientation is represented by a line…. each electron by an arrow… ex: 1s 2 2s 2 2p 6 = 1s 2s2p

17. 1s 2s2p 3) Hunds Rule - orbitals of equal energy [degenerate orbitals] are filled up equally before a 2nd electron is added. ex: 1s 2 2s 2 2p 4 a)More number of electrons with same spin increases stability b) as electrons are allowed to occupy separate orbitals, repulsion is minimized 4) Pauli exclusion Principle - two electrons cannot have the same set of 4 quantum numbers

18. 5) Exceptions to electron configuration order a) Cr - [Ar] 4s 1 3d 5 [note 1/2 filled s and d orbitals] b) Cu - [Ar] 4s 1 3d 10 [note 1/2 filled s and filled d] c) Ag - [Kr] 5s 1 4d 10 [note 1/2 filled s and filled d] 6) Electron configuration of IONS …. a) BE SURE to remove OUTERMOST electrons [valence shell electrons] ex: Zn = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 Zn +2 = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 8 Zn = 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 [numerical order] Zn +2 = 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 xWRONG!

19. (Ignore this slide) The Periodic Law History of the Periodic Table Electron Configuration and the Periodic Table Electron Configuration and Periodic Trends

20. I. History of the Periodic Table A. Mendeleyev - the ‘father’ of the modern periodic table B. Modern arrangement of the periodic table: 1) listed in order of increasing ATOMIC NUMBER 2) elements in the same GROUP have similar chemical properties C. Specific names have been assigned to specific groups 1) Alkali metals - group 1 2) Alkaline Earth metals - group 2 3) halogens - group 17 4) noble gases - group 18

21. D. Specific names are assigned to specific REGIONS of the periodic table: 1) REPRESENTATIVE ELEMENTS: all the s and p blocks 2) TRANSITION ELEMENTS: all the d block elements 3) METALS: those to the LEFT of the ‘staircase’ 4) NONMETALS: those to the RIGHT of the ‘staircase’ 5) METALLOIDS: those that BORDER the ‘staircase’

22. II. Electron Configuration and the Periodic Table A. Specific regions of the periodic table have similar outer shell electron configuration ex: What is the outer shell electron configuration for Ba? ex: What is the outer shell electron configuration for lead? ex: What is the outer shell electron configuration for silver? (think before you answer)

24. IV. The Periodic Table and Periodic Trends A.There are a variety of atomic characteristics that change in a generally consistent fashion across or down the periodic table: B. All of the properties to be examined have a pattern of either down/left OR up/right: ex:

25. C. These are the properties and their trends: 1) atomic radii (meaning how fat they are) trend: Ex: K > Na > Li …. Na > Mg > Al fewer protons (+) in the nucleus decreases effective nuclear charge (Z) more orbitals around the nucleus make it larger

26. 2) ionic radii (meaning how fat they are after losing or gaining electrons trends: Ex: Na + > Mg +2 > Al +3 ……. P -3 > S -2 > Cl -1 * Anions - greater electron repulsion as e- are added * Cations: smaller effective nuclear charge for +1 than for +3 ions more orbitals around nucleus

27. 3) ionization energy - how much ENERGY is needed to REMOVE an electron More protons increases effective nuclear charge Electrons are closer to the nucleus Discontinuity from N =>O and Be => B …. Why? (Hint: write their electron configurations)

28. 4) electron affinity - how much ENERGY is released when an electron is added to an atom Greater effective nuclear charge = more attraction e- is being added closer to the nucleus … the more energy released, the greater the EA

29. 5) electronegativity - a measure of the atom’s attraction for an electron Smaller radii and greater effective nuclear charge smaller size makes e- more strongly attracted

30. Summary: - atomic radii - ionic radii - ionization energy - electron affinity - electronegativity