1. When heated to high temps, gases give off light. If this light is passed through a slit, then through a prism or diffraction grating, the following patterns are seen: bright-line spectrum dark-line spectrum Why are there only separate (discrete) colors or lines? the lines are images of the slits Or if a light with a continuous spectrum is passed through a cold gas and then through a prism, you get:

2. Models of the atom: I. _____________________: In 1897, discovered e - ’s were ________ mass and ____________________ charged. Since he also knew that atoms as a whole were ______________, he developed the ______________________________ model: negative e- are the ____________ positive charge is ________________ distributed in a___________________ “raisin/plum pudding” J.J. Thomson low negatively neutral One _________ :atom uniformly “pudding” raisins

3. phosphorescent screen One of JJ's experiments with electrons: battery Which side of the battery was positive? electron beam

5. _____________________ : In 1909, he fired ___________ particles (positively charged ____________ nuclei) at thin gold foil:  particle Au foil only 1 in 8000 were scattered ____________ ________ were not scattered or were scattered through _____________ angles His conclusion: The ___________________________ mass is concentrated in _________________________ at the atom's _____________. He called this the ________________ of the atom. Rutherford alpha helium most backwards positively charged a very small volume only small center nucleus

7. II.As a result of Rutherford's experiment, the ___________________ model was developed: The e - 's ___________ the nucleus similar to how ________________ orbit __________________. ______________charge concentrated in the _____________ size of nucleus ~ ___________________ of `the diameter of atom positive orbit 1/10,000 solar system planets the Sun e-e- e-e- nucleus One atom:

8. _____________________with the solar system model: 1. Circular orbital motion  q _________________ 2. Accelerating q  ______________emitted from atom 3. Energy radiated  orbits will _____________________ 4. All atoms should ___________________in a short time 5. As they collapse, the e - should______________________ and the atom should _____________________emit a higher and higher ______________________ of light 6.This should produce a ____________________spectrum. but _______________ spectra were observed. accelerates radiation get smaller collapse revolve faster Problems continuously frequency continuous discrete

9. But only saw: Why? Should see:

10. III. The Bohr model for ___________________: 1. The 1 e - in H____________________ or __________ ____________the nucleus. It __________ in a ___________. 2.The e - can only be found at ______________ (certain specially allowed) distances, which are unfortunately still called __________________.  Each orbital has a _____________ number,____. a/ The orbital _____________to the nucleus is called the ____________________and has n = ____. It has the ______________ energy = ______________. b/ The orbital furthest from the nucleus has the ______________energy and has n =_____. The energy of that orbital = ____. In that case, the e - is said to be _______________, which means it is ________________ from the atom completely. hydrogen, H does not orbit around discrete move “orbitals.” n quantum ground state exists "state" closest 1 lowest -13.6 eV highest ∞ ionized. 0 removed

11. n=1 n=2 n= ∞ etc…  e- is___________ _________ state of electron n=3 The ______ e- can be found at ______ level A. Bohr model of H atom: n= 2 to ∞ are called ____________ states proton ----- = _____________ orbitals ground ionized “excited” one any

12. If an e- moves from to a ___________ energy orbital to a __________one, a photon of light is ___________ (given off). The ____________ of the emitted photon: E ph = n=1 n=2 n=3 photon _________ B. Photon _________________ : emission lower higher emitted E i - E f energy emitted

14. E i = E f = E ph = Easy way : IGNORE NEG. SIGNS AND JUST SUBTRACT!!! E ph = = E ph = E i – E f E3=E3= E 2 = E 3 – E 2 3.40 – 1.51 1.89 eV Reference Tables: page 3, top left. -1.51 eV -3.40 eV = – 1.51 – (-3.40)

15. The __________ of the absorbed photon: E ph = photon _________ If an e- moves from a ___________ energy orbital to a __________one, a photon of light is ___________ (taken in). C. Photon _________________ : absorption lower higher absorbed E i - E f n=1 n=2 n=3 energy absorbed

16. E f = E i = E ph = = E ph = E i – E f E 3 = -1.51 eV E1=E1= -13.60 eV E 1 – E 3 (ignore neg. signs) 13.60 – 1.51 12.09 eV

17. D. Energy ____________________: atom Atom __________ energy as e - moves __________ photon ___________ Emission (the ____________of light): Absorption (the ____________ of light): atom Atom _________energy as e - moves_________ photon __________ conservation birth death loses down removes energy brings energy gains up In both cases: _________________ = ___________________ energy gainedenergy lost

18. 2. No _______________________ jumps are allowed!!!  Only jumps from one ______________energy level or orbit to another ____________ energy level are allowed. 3.That is why _______________________ energy photons can be emitted or absorbed by atoms.. 4. Since E ph = hf, only certain __________________(colors) are produced. 5. That is why photon energies are ___________________(only certain values are allowed). 1. The technical term for “jumps” is____________________. E. NOTES: transitions “inbetween” allowed only certain frequencies “quantized”

19. Bigger e - jumps  more  (transitions)  more _________  _____________ frequency photons  in ___________________ and beyond E ph = E i – E f = hf Little e- jumps  less _________ (transitions)  less _________  _____________ frequency photons  in ____________________ and lower ΔEΔE = amount of e - ____________ "jump" ΔEΔE E ph blue, violet, UV ΔEΔE E ph higher red, IR lower This is true for _______________ and _______________. emission absorption

20. high f low f BIG jumps little jumps

21. _______ transitions _______ energy light involve _______ transitions _______ energy light involve little low big high Which transitions involve visible light? to the n=2 level

22. Where would these photons appear in the spectrum? And these?

23. F. ________________ : Jumps from any level to n = ___ will ___________the e - from the atom. Ionization _________________ : The _____________required to ___________an e - from an atom. What is the ionization potential for a H atom that has an electron in the ground state? What is the ionization potential for a H atom that has an electron in the n=3 state? 13.6 - 0 = 13.6 eV 1.51 - 0 = 1.51 eV Ionization ∞ remove potential energy remove

24. Notice: Mercury gas also has a fun diagram! But mercury has letters instead of numbers.

25. G. So where do _________________ (bright line) and _____________________spectra come from? The missing colors are the __________ ones that were_____________ by the gas. The heated gas absorbs, then emits only those photons from _____________ energy transitions. absorption emission Unless the source is a low-density gas, interactions with other atoms blur the lines into a _________________ spectrum. allowed continuous absorbed same

26. The same transitions produce same lines: photon absorbed photon emitted same transition

27. Each element has a _____________electron structure. The electrons make _______________transitions. Each transition produces a spectral ___________. The set of lines is a __________________for that element. Ex: Atomic absorption spectroscopy: white light gas or liquid containing ______________ elements that absorb certain photons slit _________: disperses light ___________ spectrum unique line fingerprint unknown prism absorption

28. Sun The Sun produces a continuous spectrum b/c the interaction of many gases blurs the energy levels. Atmosphere of Sun – absorbs only photons that can “jump” levels of gases in it. That is how helium was discovered. light after passing through atmosphere produces a dark line spectrum

29. Stars  broad lines  dense gas  compact star  red shifted  star moving away  blue shifted  star approaching increasing temperature

30. V. Bohr’s model could NOT explain why e - could only have ______________orbitals and energies. This was later explained by_________________________: The e - acts like a __________ and __________________ interferes with ___________ as it wraps itself around the ________________:  This can only occur at certain ______________ distances from the nucleus. Louis DeBroglie constructively nucleus itself discrete nucleus electron ________ wave orbits

31. The electrons form “standing waves” around the nucleus.

34. Electrons can act like waves. The wavelength’s of e- depend on their speed, but they are generally very small. That allows us to take pictures of very small things. fruit fly colorized house fly

35. surface of poison ivy

36. VI. The ___________Model: 1.The electron is described by a ________ function, .”  The square:  2  is the ___________________ of finding an electron at a certain position. The e - is most likely to be found where the "probability cloud" is ________________ 3.The electron is no longer thought to be located at a ________________ location, but may be ______________. 4.The locations of highest probability correspond to the positions of the old________________________. Cloud probability _________ orbitals: wave definite densest spread out Bohr orbits _________ clouds Bohr probability

38. Mass has a dual nature: particles or waves. Light has a dual nature: particles or waves. mass usually acts like a particle mass sometimes acts like a wave light usually acts like a wave light sometimes acts like a particle