CHEMISTRY

1. CHEMISTRY Part One Quantum Mechanics and Atomic Structure

2. Electromagnetic Radiation • Electromagnetic Radiation is radiant energy that travels in waves in both the electric and magnetic realms.

3. What are EM Rays? • The Spectrum of light gives us the clue. All visible light can be separated into a spectrum of colors by using a prism.

4. The Electromagnetic Spectrum • White light passing through a prism White Light Red Light Orange Light Yellow Light Green Light Blue Light Violet light

5. At The End of The Rainbow Violet Light • When white light passes • Through a prism Indigo Light Blue Light Green Light White Light Yellow Light Prism Orange Light Red Light ROY G BIV

6. A View from the Top Top View White Light beam Narrow White Light beam  Slit Prism Light Source Photographic film  Enclosed in a black box

7. Light is Energy that Travels in Waves As a light wave travels through a prism it collides with the molecules of the prism and is bent. λ = Greek letter “ Lambda “ for wavelength

8. Let’s Shed a Little Light on the Subject • Spectrum of Energy : The colors of the Rainbow all have different wavelengths

9. Waves • Electromagnetic Spectrum λ The colors in white light have different wavelengths and that is why they can be separated in a prism. If we count the number of peaks that pass by when the wave travels this is called frequency. Represented by the Greek letter “џ” λ = Greek letter “ Lambda “ for wavelength

10. Is Light the Only Path? • Visible light is not the only form of electromagnetic radiation ( EMR ). Increasing frequency Radio Micro Infrared Visible Ultra Violet X-Ray Gamma Increasing Wavelength

11. Proposition • If the atom can be excited to produce EMR then we can measure the wavelengths and determine something about the energy levels of the atom. • Lets look at what we know about waves. Wavelength Transitional velocity = speed of light ( EMR )

12. Math Relationship • The frequency and wavelength are inversely proportional. ν = c/λ λ = c/ν ν is the Greek letter “ nu “ which is used for frequency c the velocity of EMR or the speed of light = constant c = 3.00 x 108 m/s or 3.00 x 1017 nm/s

13. Lets Measure the Wavelength • If we pass an electric current through a gas the electrons absorb the energy and then tend to reach a lower energy state by releasing that energy in the form of EMR. Tends to lower energy E- EMR Higher State We can measure wavelength energy E- E-

14. Laboratory Experiment on wavelength Meter stick to measure wavelength Cathode ray tube filled with H2 <-Electric current Colored light Power Source Diffraction gradient

15. A Little View • Diagram: Lets take it from the top Diffraction Gradient λ Direction of wave Wave (Top View) As the waves pass through the DG they break up and are reinforce to show the color.

16. A Little Trig • Diagram ● 1st Spectral Line ● Y = distance to 1st line d = distance on DG Eye ‹ ● ۞ Light Source L = distance observer from source Diffraction Gradient λ = yd L

17. Does this add up? • Calculations: The diffraction gradient has 13,100 lines per inch. 1.00 in = 2.54 cm • 2.54 cm = 1.94 x 10-4cm • 13,100 lines line Therefore d = 1.94 x 10-4cm L = the distance the observer stands from the source. we will stand 100 cm; Therefore L = 100 cm λ = ydy (1.94 x 10-4cm) x 1.00 x 107 nm = 19.4 y nm L 100 cm cm cm

18. Calculations Meter Stick • Diagram ● 1st color = Red _ _ _ ___ ● Y = 32 cm Eye ‹ ● Light Source ۞ L = 100 cm Diffraction Gradient λ = 19.4 y nm/cm = 19.4 nm x 32 cm cm = 621 nm

19. So What! • What about the frequency? • v= c/λ c = velocity of EMR = 3.00 x 1017nm/s • = 3.00 x 10 17nm/s • 621 nm • = 4.83 x 10141/s ( s-1) or hertz (Hz) • cycles per second

20. Energy • It can be demonstrated that Energy due to a wave of radiant energy is inversely proportional to the wavelength • E = hc/λ • h=Planck’s constant = 4.00 x10-10 js • c=velocity of EMR = 3.00 x 1017 nm/s • Since h and c are constants we can simplify • E = (4.00 x10-10 js)(3.00 x 1017nm/s) x 1.00 kj/j=1.20 x 105 kj nm • λλ

21. Continue • If I measured a wavelength of orange to be 30.0 cm on the metric ruler then the energy could be calculated: • E = 1.20 x 105 kj nm • λ • =1.20 x 105 kj nm • 19.4 nm/cm ( 30.0 cm ) • = 206 kj

22. Remember This? • Visible light is not the only form of electromagnetic radiation ( EMR ). Increasing frequency Radio Micro Infrared Visible Ultra Violet X-Ray Gamma Increasing Wavelength

23. Let’s Stand up • Lets Graphically represent the energy levels in waves of Light E4 E3 Increasing Energy E2 E1

24. Quantum Mechanics • In studying electron structure we must consider 4 parameters of position. • Energy • Probability • Orientation in space • Movement of electrons

25. We Know about energy of electrons We measure the Energy by measuring wavelength Meter stick to measure wavelength Cathode ray tube filled with H2 <-Electric current Colored light Power Source Diffraction gradient

26. Shocking • If we pass an electric current through a pure gas the electrons absorb the energy and then tend to reach a lower energy state by releasing that energy in the form of EMR. Tends to lower energy E- EMR Higher State We can measure wavelength energy E- E-

27. Spectrum • Since the spectrum we get is a bright line spectrum we know that the electrons exist in a definite energy level as opposed to a continuous flow of levels.

28. What is the difference? • Compare Continuous Spectrum Would indicate a continuous number of energy levels. A bright line Spectrum Would indicate a definite number of energy levels.

29. Its All About the Energy • Since experiments show that the electrons in an atom produce a bright line spectrum, then we can conclude that they exist in DEFINITE energy levels in stead of a continuous set of energy levels. n = 4 – 4th energy level The symbol for the energy level is “ n “ n = 3 – 3rd energy level E- Energy of only one wavelength n = 2 – 2nd energy level E- n = 1 – 1st energy level Energy put into the system

30. First • The first parameter is that all electrons exist in different but definite energy levels. • The first quantum number is represented by the letter “ n “. • n = 1, 2, 3, 4, 5 ● ● ● ● ● Infinity

31. Second • The second parameter for understanding the position of the electron in respect to the nucleus is its probable location. Using complicated quantum mechanical equations a pattern of possible positions is plotted on a graph. The shape of the 1st energy is spherical and is called a 1s orbital

32. Movin on Up • As the energy increases the probability of different patterns and shape increases. • Consider when n = 2. Two different shapes emerge with distinct properties.

33. P Orbital • The p orbital is manifested in 3 planes. • These shapes only begin when n = 2. • The higher the energy, the greater probability of position for an electron.

34. The “d’s” • The d Orbitals are in 5 geometric spaces • They only begin when n = 3

35. 2 Down and 2 to Go • So far we have discussed 2 of 4 parameters, energy and shape of probable position. • n = energy level with values from 1 to infinity • The letter used to designate the orbital quantum number is “ l “. • l = 0, 1, 2, ● ● ● ● n-1 • The next parameter is the electron’s orientation in space.

36. Orientation We locate Orbitals with an x, y, and z axis py px x The p-orbital is located along and x,y,z plane. z pz y

37. Quantum Values • The orientation in space is referred to as the magnetic quantum number. • The values of this are determined by the l quantum number. • ml = -l…0…+ l • If l = 0 then ml = 0, If l = 1 then ml = -1,0,1

38. Lets Put a Spin on It • The Final parameter we need to discuss is what the electron is doing. • The electron is not stagnate but we know from experiments it is spinning. The symbol for the spin QN is ms The values for msare ± 1/2 for each ml E-

39. All together now!

40. Allowed Values 1s2 2s2 2p6 3s23p63d10 1 2 2 4 3 0 ? 0 1 0 1 2 -2 -1 0 1 2 -1 0 1 0 0 -1,0,1 0 ? ±1/2 ±1/2 ±1/2/ml ±1/2 ±1/2 ±1/2 ?

41. Let’s Get Graphic Sub Level 4f14 • Energy Diagram: 4d10 Energy Level 4p6 n=4 3d10 4s2 n=3 3p6 3s2 2p6 n=2 Energy 2s2 n=1 1s2

42. Sequence • We would expect that the sequence of orbital filling would be in order, however nature doesn’t follow our logic but has its own. There are explanations for these variations which at closer inspection make sense. • THE ORDER • 1s • 2s 2p • 3s 3p • 4s 3d 4p • 5s 4d 5p • 6s 4f 5d 6p • 7s 5f 6d 7p We sit at the Periodic Table

43. And the Order is • The Periodic Table p6 S1 S2 1 p5 p1 p2 p3 p4 2 The “d’s” 3 4 5 6 7 The “f’s”

44. Atomic Structure • Electron Configuration Notation (ECN ) 1S1 1S2 1S22s1 1S22s2 1S22s22p1

45. And Sole On • Continue with ECN 1S22s22p2 1S22s22p3 1S22s22p4 1S22s22p5 1S22s22p6

46. Let’s Get to the Core • The ECN Core Method • Since the next element in our series is Element # 11, Na it would have the following ECN • 1s22s22p63s1 [1020Ne]3s1 This is the Core method = Every element in the 3rd row will have the same core This is the structure of Ne

47. Down to the Core • Continue with Core ECN [1020Ne] 3S1 [1020Ne] 3S2 [1020Ne] 3S23p1 “ 3S23p2 “ 3S23p3

48. Another Method? • In order to understand exactly what the structure of an atom is, sometimes we have to approach it another way. • ELECTRON ORBITAL NOTATION ( EON ) • When representing Orbitals and electrons in the Orbitals we use brackets or circles for the Orbitals and arrows or lines to represent the electrons. • [ ] Ο E- E- The up and down arrows indicate opposite spins The right and left lines indicate opposite spins

49. Series Four • A “d” transition [1840Ar] 4s 3d 4p ΟΟΟΟΟΟ ΟΟΟ [1840Ar] 4s 3d 4p ΟΟΟΟΟΟ ΟΟΟ [1840Ar] 4s 3d 4p ΟΟΟΟΟΟ ΟΟΟ [1840Ar] 4s 3d 4p ΟΟΟΟΟΟ ΟΟΟ

50. Continue • A “d” transition [1840Ar] 4s 3d 4p ΟΟΟΟΟΟ ΟΟΟ [1840Ar] 4s 3d 4p ΟΟΟΟΟΟ ΟΟΟ [1840Ar] 4s 3d 4p ΟΟΟΟΟΟ ΟΟΟ Hund’s Rule: There is a stability associated with a ½ filled or filled d orbital.