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chem.uncc/faculty/murphy/1251/slides/C12/sld003.htm

http://www.chem.uncc.edu/faculty/murphy/1251/slides/C12/sld003.htm. The ratio of masses of one element that combine with a constant mass of another element can be expressed in ratios of small whole numbers. Atomic models. Electrons. Bohr’s atomic model (1913)-

hayley-hill
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chem.uncc/faculty/murphy/1251/slides/C12/sld003.htm

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  1. http://www.chem.uncc.edu/faculty/murphy/1251/slides/C12/sld003.htmhttp://www.chem.uncc.edu/faculty/murphy/1251/slides/C12/sld003.htm The ratio of masses of one element that combine with a constant mass of another element can be expressed in ratios of small whole numbers.

  2. Atomic models

  3. Electrons Bohr’s atomic model (1913)- electrons revolve around the nucleus in distinct energy levels.

  4. How light is emitted. . . • Excited state- electron(s) in higher energy levels than at ground state (lowest energy state). • Energy is emitted when the electron(s) return to ground state. • The frequency of the radiation emitted depends on the difference between the higher and lower energy levels.

  5. Frequency-the number of wave cycles passing a point in a period of time. As frequency increases, wavelength decreases (C=3.0 x 108 m/s)

  6. Light of a particular wavelength (λ) has a particular frequency (v) and energy. • E = h∙v and c = λ∙v • If v, λ, or E are known, the other two can be calculated. c=3.0 x 108 m/s speed of light h=6.63 x 10-34 joule-sec Planck’s constant E is the energy of one photon of light

  7. Yellow light given off by a sodium vapor lamp has a wavelength of 589 nm. What is the frequency of this radiation? • v = c/λ • = 3.0 x 108 m/sx109 nm= 5.09x1014 s-1 589nm 1 m

  8. Calculate the energy of one photon of yellow light whose wavelength is 589nm. E = hv = (6.626 x 10-34J∙s)(5.09x1014 s-1) = 3.37 x 10-19 J Substitute v= c/λ in E = h∙v and you get E = h∙c λ

  9. Wave-particle duality of light • Planck stated that energy is radiated in discrete packets called quanta. A photon is a quantum of light having the energy h∙v. • Light’s particle nature is seen in its ability to eject electrons from a surface (photoelectric effect), and by the emission spectra of elements.

  10. Principal Quantum Number (n) • Tells its energy level and distance from the nucleus • The maximum number of electrons at each energy level is 2n2. at n = 1, there can be 2(1)2=2 electrons at n = 2, there can be 2(2)2=8 electrons at n = 3, there can be 2(3)2=18 electrons

  11. angular quantum number (l) Sublevel • tells the shape of the electron cloud. S spherical (l = 0), P polar (l = 1), D cloverleaf (l = 2) F (l = 3) (l) can be any integer between 0 and n - 1

  12. magnetic quantum number (m) • describes the orientation in space of a particular orbital • One pair of electrons can occupy each orbital s sublevels have one orbital p sublevels have 3 orbitals d sublevels have 5 orbitals f sublevels have 7 orbitals m can be any integer between -l and +l

  13. For p orbitals (l = 1), • there are three possible orientations, • so m can be -1, 0, or 1.

  14. Spin The forth quantum number (s) indicates the direction of spin on the electron. Ih • s = +½ or -½ Pauli Exclusion Principlestates that no two electrons in an atom can have the same set of four quantum numbers. The two electrons in an orbital must have opposite spins.

  15. AllowableCombinations of Quantum Numbers

  16. Example Quantum Number Problem List the quantum numbers of all 10 electrons in a neon atom. 1s :   1, 0, 0, ±½ 2s: 2, 0, 0, ±½ 2p: 2, 1, -1, ±½ 2, 1, 0, ±½ 2, 1, 1, ±½

  17. Which of the following sets of quantum numbers are possible? 1, 0, 0, ½ Yes 1, 3, 0, ½ No, l must be less than n Yes 4, 2, -2, -½ No, -l <m < +l 3, 1, 2, ½ 3, 2, 1, 0 No, spin is never an integer

  18. Electrons occupy the lowest energy level available first (Aufbau Principle). Electron Configuration Notation • H has a 1s electron • He has two 1s electrons, or 1s2 • Li has two 1s and a 2s electron, or 1s22s1 Electron Dot Notation- show only the electrons in the outermost energy level H∙ He: Li∙ Be: Mg:

  19. 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 6f 7s 7p 7d 7f Sublevels fill in order of increasing energy. 1s2s2p3s3p4s3d4p5s4d5p6s4f5d6p7s5f6d7p

  20. Predicting electron configurations from the periodic table.

  21. Electron configuration notation Helium has 2 electrons, so its electron configuration would be 1s2 Li 1s22s1 N 1s22s22p3 Ne 1s22s22p6 Na 1s22s22p63s1 or [Ne]3s1

  22. Orbital notation 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. 1s 2s 2p N (7)EEhhh F (9) EEEEh

  23. Paramagnetic- an atom having one or more unpaired electrons • Diamagnetic- all electrons are paired Which elements in period 2 are diamagnetic? Be and Ne

  24. Ways to represent titanium 1s2 2s2 2p6 3s2 3p6 4s2 3d2 electron configuration EEEEEEEEEEhh__ __ __ 1s 2s 2p 3s 3p 4s 3d Ti: 22 2 8 10 2

  25. Ways of separating a mixture distillation chromatography

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