Electrons in Atoms: Wavelength, Frequency, and Electron Configuration

1. Chapter 5“Electrons in Atoms”

2. Terms Wavelength Frequency Amplitude Electromagnetic spectrum Atomic orbital Excited state Ground state Electron configuration Valence electron Take 15-20 minutes and create a Vocabulary Poster using a Chapter 3 Term

3. Parts of a wave Crest Wavelength Amplitude Trough Origin

4. Wave • Wavelength (represented by λ, the Greek letter lambda) is the shortest distance between equivalent points on a continuous wave.

5. Wave • Frequency (represented by ν, the Greek letter nu) is the number of “waves” that pass a given point per second. • One hertz (Hz), the SI unit of frequency, equals one wave per second.

6. Wave • In calculations, frequency is expressed with units of “waves per second,” example: • ( ) • or (s–1). • C = speed of wave = 3.00 x 108m/s

7. Calculating Wavelength of an EM Wave • What is the wavelength of a microwave having a frequency of 3.44 x 109 Hz? 1. Rearrange

8. Calculating Wavelength of an EM Wave • Substitute cand the microwave’s frequency, v, into the equation. • Divide the values to determine wavelength, λ, and cancel units as required.

9. Electromagnetic Spectrum: EM spectrum Used to describe electromagnetic radiation Includes a wide range of wavelengths and frequencies. Visible light are the colors we see

10. STOP Do practice problems on white boards. Then, create your own EM Spectra. Make interpretations of how an EM Spectra reads to you.

11. Question 1 A helium-neon laser emits light with a wavelength of 633 dm. What is the frequency of this light? Question 2 What is the wavelength of X rays having a frequency of 4.80 x 1017 Hz?

12. Question 3 A laser emits light with a wavelength of 5.65x102 mm. What is the frequency of this light? Question 4 What is the wavelength of a ray that has a frequency of 8.94 x 1016 Hz?

13. Section 5.2 • Quantum Theory and The Atom

14. Energy states • The lowest energy state is called its ground state. • When an atom gains energy, it in an excited state.

15. Quantum Numbers • A quantum number, n, is assigned to each orbit. • For the first orbitn = 1, the second orbit, n = 2; and so on.

16. Bohr said that: • Energy related to orbit • Electrons cannot exist between orbits • Higher energy level : Further away from nucleus • Maximum number of electrons in outermost orbital the energy level is stable (unreactive)

17. Bohr’s Model Nucleus Nucleus Electron Electron Orbit Orbit Energy Levels Energy Levels

18. Changing the energy A hydrogen atom, with only one electron, and in the first energy level. Ground state

19. Heat, electricity, or light can move the electron up to different energy levels. The electron is now said to be “excited” Changing the energy

20. As the electron falls back to the ground state, it gives the energy back as light Changing the energy

21. Line spectrum of various elements Carbon Helium

22. STOP • Flame Test

23. Ground-state Electron Configuration The arrangement of electrons in an atom is the electronconfiguration. Low-energy systems are more stable.

24. Orbitals on the PT • In order of increasing energy, the sequence of orbitals is • s, p, d, and f. • S – 2 electrons • P – 6 elections • D – 10 electrons • F – 14 electrons

25. Writing Electron ConfigurationUse your PT Number row. Orbital Electrons = atomic number

26. PRACTICE How would you write the electron configuration for Sodium? What’s the atomic number? 11, so the superscript numbers should add to 11 1s22s22p63s1 Do the superscript numbers should add to 11?

27. Ground-state Electron Configuration • Three rules apply • The aufbau principle/rule • The Pauli exclusion principle/rule • Hund’s rule • These all define how an electron is arranged.

28. AUFBAU PRINCIPLE • States: each electron occupies the lowest energy orbital available. • Step 1: determine ground-state by learning the sequence of atomic orbital's • The aufbau Diagram

29. The aufbau Diagram Each box represents an atomic orbital. Fig: 5.17 Page 135

30. ELECTRON CONFIGURATIONS… Pauli Exclusion Principle- at most 2 electrons per orbital - different spins

31. ELECTRON CONFIGURATIONS Hund’s Rule- When electrons occupy orbitals of equal energy, they don’t pair up until they have to.

32. ELECTRON CONFIGURATIONS Let’s write the electron configuration diagram for Phosphorus We need to account for all 15 electrons in phosphorus

33. The first two electrons go into the 1s orbital Notice the opposite direction of the spins only 13 more to go... 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Increasing energy 3s 2p 2s 1s

34. The next electrons go into the 2s orbital only 11 more... 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Increasing energy 3s 2p 2s 1s

35. 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Increasing energy 3s 2p 2s 1s • The next electrons go into the 2p orbital • only 5 more...

36. 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Increasing energy 3s 2p 2s 1s • The next electrons go into the 3s orbital • only 3 more...

37. 7p 6d 5f 7s 6p 5d 6s 4f 5p 4d 5s 4p 3d 4s 3p Increasing energy 3s 2p 2s 1s • The last three electrons go into the 3p orbitals. • 3 unpaired electrons

38. Noble Gas Notation Travel back to the last noble gas prior to your element. Sodium last pasted Ne therefore we can write its electron configuration like… [Ne] 3s1 Reads: go to Neon then to the 3rd row in the s orbital 1 element in.

39. VALENCE ELECTRONS Define as the electrons in the atom’s outermost orbitals. Example: Sulfur has 16 electron total. Representative elements go by the column number Transition metals are given

40. Valance Electrons 1 2 3 4 5 6 7 8

41. ELECTRON-DOT STRUCTURE Include: element’s symbol = inner-electrons Surrounded by dots = valence electrons Check out Table 5.5 as a Reference

42. ELECTRON-DOT STRUCTURE O Cl

43. Classwork Create a poster of your element Include… symbol name electron configuration Aufbau diagram electron-dot structure Noble gas configuration if possible