1. Chapter 5 Electrons in Atoms

2. Wave Nature of Light Wavelength (λ) – shortest distance between equivalent points on a continuous wave (unit: m or nm) Ex: Crest to Crest or Trough to Trough

3. Wave Nature of Light Frequency (ν) – the number of waves that pass a given point per second (unit: Hz or 1/s) 1 Hertz (Hz) = 1 wave per second

4. Electromagnetic Radiation form of energy with wave-like behavior Wavelength and Frequency Relationship: Inverse Relationship: Long Wavelength mean Low Frequency

5. Speed of Light ALL electromagnetic radiation moves at the speed of light speed of light = c = 3.0 x 10 8 m/s Formula: c = λν = (wavelength) x (frequency)

6. Sample Problem Microwaves are used to cook food and transmit information. What is the wavelength of a microwave that has a frequency of 3.44x10 9 Hz? Given: ν = 3.44 x 10 9 Hz Find: λ = ? Equation:

7. Electromagnetic Spectrum shows all forms of electromagnetic radiation (pg 139)

8. Electromagnetic Spectrum shows all forms of electromagnetic radiation (pg 139)

9. Emission Spectrum Ground State: lowest, most stable energy state of an electron Excited State: has more energy than the ground state Photon: particle of electromagnetic radiation Light is both a particle and a wave

10. Photon Every element has its own specific atomic emission spectrum When an excited electron returns to the ground state, it gives off a photon of electromagnetic radiation.

11. Electrons are located in the electron cloud. The electron does not have a definite path nor can it be specifically located, but we can predict its whereabouts based on probabilities called orbitals

12. Quantum Theory and Numbers gives an electron’s position in an atom 4 quantum numbers n l m s

13. Quantum Numbers NameSymbolDefinitionDetails n l m s Indicates the orientation in space (dependent on the shape) Subshell indicates the shape of the orbital Indicates the average distance of the electron from the nucleus Indicates the direction of spin of the electron n is the period number (a number between 1 and 7) Shapes are labeled by letters (s,p,d,f) s = 1 orientation p = 3 orientations d = 5 orientations f = 7 orientations Spin is either +1/2 or -1/2 Orbital QN Magnetic QN Spin QN Principle QN If we compared Quantum Numbers to an address then state city street Side of street

14. Important note: EVERY electron in an atom has a specific, unique set of the four quantum numbers!

15. n (Principle Quantum #) Discovered and presented by Niels Bohr in the Bohr model of the atom Indicates: The distance from the nucleus The size/volume of the electron’s orbital The atom’s major energy levels The further the electron is from the nucleus the greater n will be

16. n (Principle Quantum #) The larger the n the greater volume of the electron cloud and the greater the energy n can be a number between 1 and 7

17. l (Orbital Quantum #) Indicates the shape of the orbital (the sub shell) s p d f

18. m (Magnetic Quantum #) The shape is determined by l but m determines how the shape is oriented in space. s orbital – spherical Only 1 orientation

19. m (Magnetic Quantum #) The shape is determined by l but m determines how the shape is oriented in space. p orbital: “dumbbell” 3 orientations

20. m (Magnetic Quantum #) The shape is determined by l but m determines how the shape is oriented in space. d orbital: 5 orientations

21. m (Magnetic Quantum #) The shape is determined by l but m determines how the shape is oriented in space. f orbital: 7 orientations

22. m (Magnetic Quantum #) Each orbital orientation can hold only 2 electrons: s : 1 orientation = 2 total electrons p : 3 orientations = 6 total electrons d : 5 orientations = 10 total electrons f : 7 orientations = 14 total electrons

23. s (Spin Quantum Number) Indicates which direction the electron spins The 2 electrons in an orbital orientation will have opposite spins ( + ½ or – ½)

24. Pauli Exclusion Principle Each electron in an atom has a unique set of quantum number therefore, a maximum of two electrons can occupy a single atomic orbital

25. Electron Configuration Quantum numbers are used to write electron configurations of an element Hydrogen H Atomic number: 1 1s 1 n Shape determined by l # of electrons

26. Aufbau Principle Each electron occupies the lowest energy orbital available

27. Two Methods of Writing Configurations Write the configuration of Na: 1s 2 2s 2 2p 6 3s 1 Na has 11 electrons The electrons from the configuration should add up to 11. Method 1 Remember: s can hold 2 electrons, p 6, d 10 and f 14

28. Two Methods of Writing Configurations Use the periodic table Write the electron configuration for Ar: Ar Always start at 1s 1s 2 2s 2 2p 6 3s 2 3p 6 Argon’s atomic number is 18 The superscripts from the electron configuration added equal 18.

29. Examples Write the electron configuration for the following elements: C: P: Ag: Rn: 1s 2 2s 2 2p 6 3s 2 3p 3 1s 2 2s 2 2p 2 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 9 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 6

30. Orbital Notation Electron configurations can be written as diagrams Orbital Notation diagrams show the individual orientations and the electrons that fill them. Hund’s Rule: fill orbitals so that the number of unpaired spins is maximized; electrons will fill orbitals before pairing up

31. Orbital Notation Write the orbital notation for Carbon: Electron configuration: 1s 2 2s 2 2p 2 1. Write a line for each orientation associated with a orbital shape: s = 1, p = 3, d = 5, f = 7 2. Fill electrons in each shape. Place a single electron in each orbital before pairing them up. 1s2s2p

32. Examples Write the orbital notation for the following elements: C: P: Ag: Rn:

33. Noble Gas Configuration All electron configurations can be abbreviated… Electron Configuration for Ca is: Noble gas configuration for Ca is:

34. Lewis Dot Diagrams The outer electrons are use to draw Lewis Dot Diagrams The number of electrons in the highest principle quantum number (largest “n” values) determines the number of electrons in the diagram

35. Examples H 1s 1 Be 1s 2 2s 2 N 1s 2 2s 2 2p 3 Ne 1s 2 2s 2 2p 6 5 electrons 2 electrons 1 electron 8 electrons Ne :: : : H. N :... Be..