Chapter 7: Atomic Structure & Periodicity

1. Chapter 7: Atomic Structure & Periodicity • Wave Theory of Electromagnetic Radiation • Particle Theory of Electromagnetic Radiation (UV Catastrophe & Photoelectric Effect) • Particle and Wave Theories of Matter (deBroglie wavelengths & Uncertainty Principle) • Atomic Spectra & Bohr’s Model of the Atom • Quantum Mechanical Model of the Atom (quantum numbers, orbitals) • Electron Spin & Pauli Exclusion Principle • Electron Configurations • Periodic Trends in IE, EA, and Atomic Radius • Relationship between Electron Config & Reactivity: Group IA

2. The Electromagnetic Spectrum http://www.flandrau.org/WEBSITE/Background.htm

3. Separating Wavelengths of Light http://www.phys.ufl.edu/~avery/course/3400/light/prism.gif

4. Example 1 What is the frequency of the red laser light used in grocery store scanners if it has a wavelength of 6328A? 1A = 10-10 m. Answer: 4.741 x 1014 /s

5. Example 2 What wavelength of electromagnetic radiation is broadcast by KCRW at 89.9 MHz? Answer: 3.34 m

6. The Ultraviolet Catastrophe http://www.chem.ufl.edu/~chm2040/ Images/Chapter/Chap_9/g13f5.gif

7. The Photoelectric Effect http://www.astro.queensu.ca/~hanes/ p014/Notes/Figures/PE_Effect.gif

8. Example 3 The work function for Cr metal is 652.7 kJ/mole. Find: • The energy (in J) needed to remove an electron from one atom of Cr. • The minimum energy (in J) a photon must have to ionize Cr. • The maximum wavelength (in nm) of light that can ionize Cr. Answers: a. 1.084 x 10-18 J / atom b. 1.084 x 10-18 J c. 183.4 nm

9. Example 4 The work function of sodium metal is 496 kJ/mole. What is the maximum wavelength of light that can ionize sodium? Can light at 255 nm ionize sodium? Answer: 241 nm; no

10. Example 5 Challenge Problem: When light with a wavelength of 86.0 nm is incident upon a metal surface, electrons are ejected with a velocity of 4.25 x 105 m/s. What is the work function of this metal in kJ/mole? Answer: 1342 kJ/mole

11. Atomic Spectra,Emission & Absorption http://www.cbu.edu/~jvarrian/252/ emspex.jpg

13. Example 6 According to Bohr’s theory, what is the energy of an electron in the n=5 orbit of a hydrogen atom? Answer: E5 = -8.72 x 10–20 J

14. Example 7 How much energy is lost by an electron when it moves from the n=3 orbit to the n=1 orbit of a hydrogen atom? What wavelength of light will be emitted by the electron when it makes this transition? Answer: 1.938 x 10-18 J; 103 nm

15. Example 8 A spectral line in the Balmer series for hydrogen occurs at 397 nm. What electronic transition is responsible for this line? Answer: n=7  n=2

16. Electron Orbits as Standing Waves

17. Example 9 What is the deBroglie wavelength of: • A baseball with a mass of 140 g and a velocity of 25 m/s? • An electron with a velocity of 1.0 x 104 m/s? Answer: a) 1.9 x 10-34 m b) 7.3 x 10-8 m

18. Example 10 What is the minimum uncertainty we can have in the position of an electron moving at a velocity of 5.0 x 105 m/s? The mass of an electron is 9.109 x 10-31 kg. Hint: Start by calculating the uncertainty in the velocity! Answer: 1 x 10-8 m or 10 nm

19. A 1s orbital (n=1, l=0, ml=0)

20. s orbitals

21. The 2p Orbitals (n=2, l=1, ml=-1,0,1)

22. Penetration of Inner Electron Shells by Outer Electrons

23. Example 11 Write the electron configurations for the following atoms. Noble gas abbreviations are okay for inner core electrons. a) F b) P c) Ti d) Cu

24. Example 12 State whether each of the following atoms is paramagnetic or diamagnetic: • N • Fe • Ca

25. Trends in Atomic Radius (Size)

26. Trends in Ionization Energy

27. Trends in Electron Affinity