Chapter 13: Electrons in Atoms

1. Chapter 13: Electrons in Atoms

2. Waves • Properties- • () Frequency-number of waves that pass a given point per unit of time. • () Wavelength- distance between similar points in a set of waves (crest to crest.)

3. Properties of waves, cont. • Amplitude- distance from crest or trough to the normal • Energy- Waves do not carry energy, they transmit energy. The amount of energy determines the amplitude and the frequency.

4. Energy vs. Amplitude • Energy and amplitude are DIRECTLY related. As energy increases, amplitude increases. As energy decreases, amplitude decreases • Review waves at home: http://www.glenbrook.k12.il.us/gbssci/phys/Class/waves/u10l2a.html

5. Speed of the wave • Speed = frequency x wavelength=  • S=as frequency increases wavelength decreases • inverse relationship- what does inverse mean? • c = Speed of light 3.00 x 108m/s • (in a vacuum)

6. Practice Problems • What is the wavelength of a radio wave whose frequency is 1.01 x 108 Hz? Remember scientific notation-here it is again… Speed = wavelength x frequency

7. Practice Problems • What is the frequency of a green light which has a wavelength of 4.90 x 10-7 m? Speed = wavelength x frequency

8. Practice Problems • An X-ray has a wavelength of 1.15 x 10-10 m. What is its frequency? Check your answer!

9. Light as Particles • quantum – term coined by Max Planck in the early 1900’s; it is the minimum amount of energy that can be gained or lost by an atom. • Planck’s constant (h) relates energy and frequency. • h = 6.626 x 10-34 Js • E = h • Frequency and energy are DIRECTLY related.

10. Electromagnetic Spectrum • Page 120 Frequency and energy have a direct relationship.

11. About Light • Light- Characteristics of light waves Visible light when bent (refracted) gives different colors, each color corresponds to a different frequency. (pg 120) • R O Y G B I V • (E) (E) • Light travels in bundles called photons. • Energy = Planck's constant x frequency • E=hv (unit for energy is the joule)

12. Photon • photon – a particle of electromagnetic radiation with no mass that carries a quantum of energy; a bundle of energy; a stream of tiny particles • the idea of a photon was developed when Einstein, in 1905, said that electromagnetic radiation has both wavelike and particlelike natures

13. Quantum leap • When an electron is excited, by heat or electricity, it absorbs energy and jumps to a higher energy level. When the electron jumps down to a lower energy level it gives off energy in the form of light. Each jump is a different color. • The colors given off are called the bright line spectra; it acts as a finger print for the element. • Remember the flame tests we did?

14. Atomic Spectra http://www.physics.lsa.umich.edu/demolab/graphics2/7b10_u2a.jpghttp://www.physics.lsa.umich.edu/demolab/graphics2/7b10_u2b.jpg

15. Flame tests • Show colors unique to each element http://www.unit5.org/christjs/flame%20tests.htm

16. Bohr Models • Because of the quantum leap Bohr theorized that the electron traveled in different energy levels. • Bohr video Must watch at school! • Try this video! • A bohr diagram gives us a fair idea about where electrons are in their clouds • The shells are labeled K, L, and M • K has 2 e-, L has 8 e-, M has 18 e-

17. Bohr Diagrams • Try this practice site • Draw a diagram of Carbon, Magnesium, and Silicon

18. Modern Concept:Quantum Mechanical Model • Bohr’s Model had two problems: • Electrons are always moving • Tests to “see” electrons move electrons • Bohr's theory only works well in explaining one or two electrons. • Modern theory is based on...

19. Origins of Quantum Model 1. de Broglie-Dual nature of matter which says that that light can act like a particle and that particles can act like light waves. 2.Heisenberg's uncertainty principle - It is impossible to know both the speed and location of an electron at the same time. • Schodinger wave equation-predicts the location of the electron most of the time. Dealt with the probability of finding a blurry electron cloud which he called an orbital. • Orbital- a region of space in which the electron can be found 90% of the time.

20. Quantum numbers • From Schrodinger'sequation each electron is assigned a set of quantum numbers to distinguish each from all other electrons (address)no 2 electrons have the same set of quantum numbers • Pauli's Exclusion Principle - Electrons in the same orbital must have opposite spin. (an orbital will hold only ____ electrons.) http://nobelprize.org/physics/laureates/1933/schrodinger-bio.html

21. Quantum Numbers Decoded "Never say, 'I tried it once and it did not work.'" -- Ernest Rutherford Remember an orbital can only contain 2 electrons!

22. Pictures of Orbital shapes P orbitals (2 of3) S orbital D orbitals (1 of 5) http://www.colorado.edu/physics/2000/elements_as_atoms/orbitals.html

23. Labeling Electrons • Orbital filling diagram and electron configuration. Both methods use the following rules. • Aufbau Principle- fill lowest energy level first • Hund's Rule- fill equal orbitals before pairing up. • http://intro.chem.okstate.edu/WorkshopFolder/Electronconfnew.html • http://tinyurl.com/9v6zu

24. Electron Configurations • The Electron Dorm • Always follow the order • 1s 2s 2p3s 3p 4s 3d 4p5s 4d 5p6s 4f 5d 6p7s 5f 6d 7p

25. Orbital Diagramsand Electron Configurations

26. Let’s Practice • Do the electron Configurations of elements 11-19

27. Lewis Dot Structures • The dots around the atom’s symbol represent the electrons in the atoms outermost energy level. • There will be no more than 8 • Note how these dot structures follow the main group elements (A columns) of the periodic table.

28. IA IIA IIIA IV A VA VIA VIIA VIIIA Lewis Dot Structures See your teacher to learn what the dot structures look like or look them up in your book! Elements with fewer than 4 electrons in the outer shell tend to lose electrons whereas elements with more than 4 outershell electrons tend to gain electrons!

29. Practice Problem 1: • Write the orbital filling diagram • Write the electron configuration • Write the noble gas notation. • How many electrons in the outer shell • In what period and group does this element appear on the periodic table? • Metal, nonmetal or metalloid? • Electron dot structure? • Gain or lose electrons? • Highest energy level filled?

30. Practice Problem 2: • Write the orbital filling diagram • Write the electron configuration • Write the noble gas notation. • How many electrons in the outer shell • In what period and group does this element appear on the periodic table? • Metal, nonmetal or metalloid? • Electron dot structure? • Gain or lose electrons? • Highest energy level filled?

31. Practice Problem 3: • Write the orbital filling diagram • Write the electron configuration • Write the noble gas notation. • How many electrons in the outer shell • In what period and group does this element appear on the periodic table? • Metal, nonmetal or metalloid? • Electron dot structure? • Gain or lose electrons? • Highest energy level filled?

32. Answer to Practice Problem • An X-ray has a wavelength of 1.15 x 10-10 m. What is its frequency?