1. Chapter 5: Electrons in Atoms
Revising the atomic model
Electron arrangement in atoms
Atomic emission spectra and the quantum mechanical model

2. Learning Targets You will:
Determine the energy levels, sublevels and orbitals of electrons in an atom.
Determine how to write electron configuration and orbital notation for atoms and ions.

3. Atom Models …
Rutherford: couldn’t explain chemical properties of elements
Bohr: explained how energy levels of electrons in an atom change when the atom emits light
Schrodinger: devised and solved mathematical equation describing electron behavior in atom
Restricts energy of electrons to certain values
Doesn’t specify exact path electron takes around nucleus
Calculations show previous models didn’t always correctly describe electron motion
You will determine the energy levels, sublevels and orbitals of electrons in an atom.

4. Quantum Mechanical Model
Probability of finding an electron represented as fuzzy, cloudlike region
Cloud more dense when probability high
Atomic orbital is pictorially a region of space where high probability of finding electron
You will determine the energy levels, sublevels and orbitals of electrons in an atom.

5. Quantum Mechanical Model
Energy levels labeled by principal quantum numbers (n) and assigned values of 1, 2, 3, 4 and so on
Energy levels within principal energy level are sublevels
Each sublevel corresponds to one or more orbitals of different shapes
You will determine the energy levels, sublevels and orbitals of electrons in an atom.

6. Summary of energy levels and sublevels
You will determine the energy levels, sublevels and orbitals of electrons in an atom.

7. Atomic Orbitals
Principal quantum number, n, = # sublevels w/in principal energy level
# orbitals in principal energy level = n2
Maximum of 2 electrons can occupy an orbital
Maximum number of electrons that can occupy an energy level = 2n2
Example:
Calculate the maximum number of electrons in the 5th principal energy level (n = 5).
The maximum number of electrons that can occupy a principal energy level is given by the formula 2n2.
If n = 5, 2n2 = 50.
You will determine the energy levels, sublevels and orbitals of electrons in an atom.

8. Sublevels and Energy Levels
You will determine the energy levels, sublevels and orbitals of electrons in an atom.

9. What causes atomic emission spectra?
Table talk …
What causes atomic emission spectra?
When atoms absorb energy, their electrons move to higher energy levels. These electrons lose energy by emitting light when they return to lower energy levels.
No two elements have the same emission spectrum.
You will determine the energy levels, sublevels and orbitals of electrons in an atom.

10. You will determine the energy levels, sublevels and orbitals of electrons in an atom.
What we saw in the lab …

11. c = ln Nature of light Amplitude = wave’s height from zero to crest
Wavelength = distance b/t crests
Frequency = # wave cycles to pass given point/unit of time
Frequency and wavelength inversely proportional
Product of frequency and wavelength = constant (c), speed of light
c = ln

12. Nature of Light
Electromagnetic radiation includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, x-rays and gamma rays
All waves travel at a speed of 3.00 x 108 m/s

13. Example
Calculate the wavelength of the yellow light emitted by a sodium lamp if the frequency of the radiation is 5.09 × 1014 Hz (5.09 × 1014/s).
c =   
𝑐 𝑣 = 
3.00 x 10^8 m/s 5.09 x 10^14 Hz = 
5.89 x 10-7 m = 

14. What is the frequency of a red laser that has a wavelength of 676 nm?
Try on your own
What is the frequency of a red laser that has a wavelength of 676 nm?
c =   
𝑐  = 
676 nm  1 m 1 x 10^9 nm = 6.76 x 10-7 m
3.00 x 10^8 m/s 6.76 x 10^−7 m = 
4.44 x 1014 Hz = 

15. Quantum Concept and photons
German physicist Max Planck showed mathematically that the amount of energy (E) absorbed or emitted is proportional to the frequency of radiation ().
The constant (h) has a value of x Js and is called Planck’s constant

16. Example E = h   E = 6.626 x 10-34 Js  3.20 x 1011/s
What is the energy of a photon of microwave radiation with a frequency of 3.20 × 1011/s?
E = h  
E = x Js  3.20 x 1011/s
E = 2.12 x J

17. Try on your own
What is the frequency of a photon whose energy is x 10–17 J?
E = h  
𝐸 ℎ = 
1.166 x 10^−17 J x 10^−34 Js = 
1.760 x 1016 Hz = 

18. Table talk …
What are the three rules for writing the electron configurations of elements?
Three rules—the aufbau principle, the Pauli exclusion principle, and Hund’s rule—tell you how to find the electron configurations of atoms.
Aufbau principle: electrons occupy orbitals of lowest energy first before filling higher energy levels
Pauli exclusion principle: two electrons must have opposite spins to occupy the same orbital
Spin is a quantum mechanical property of electrons
A vertical arrow indicates an electron and its direction of spin
Hund’s rule: every orbital is singly occupied with one electron before any orbital is doubly occupied, all electrons in singly occupied orbitals have the same spin.
You will determine how to write electron configuration and orbital notation for atoms and ions.

19. Electron Configurations
Convenient shorthand method involves writing energy level and symbol for every sublevel, then indicate the number of electrons w/superscript
Sum of the superscripts = # electrons in atom
You will determine how to write electron configuration and orbital notation for atoms and ions.

20. Electron Configurations
You will determine how to write electron configuration and orbital notation for atoms and ions.

21. Write the electron configuration for the following atoms:
Examples
Write the electron configuration for the following atoms:
hydrogen
nitrogen
aluminum
Answers:
1s1
1s2 2s2 2p3
1s2 2s2 2p6 3s2 3p1
You will determine how to write electron configuration and orbital notation for atoms and ions.

22. Electron Configurations
You will determine how to write electron configuration and orbital notation for atoms and ions.

23. Write the electron configuration for the following atoms:
More Examples
Write the electron configuration for the following atoms:
helium
oxygen
silicon
Answers:
1s2
1s2 2s2 2p4
1s2 2s2 2p6 3s2 3p2
You will determine how to write electron configuration and orbital notation for atoms and ions.

24. Electron Configurations
You will determine how to write electron configuration and orbital notation for atoms and ions.

25. Write the electron configuration for the following atoms:
Try on your own
Write the electron configuration for the following atoms:
sodium
phosphorus
potassium
Answers:
1s2 2s2 2p6 3s1
1s2 2s2 2p6 3s2 3p3
1s2 2s2 2p6 3s2 3p6 4s1
You will determine how to write electron configuration and orbital notation for atoms and ions.

26. Electron Configurations
You will determine how to write electron configuration and orbital notation for atoms and ions.

27. Orbital Notation
Orbital notation is a way of drawing electron configurations
A box or blank indicates the space for an orbital
Remember an orbital can hold two electrons
An orbital will correspond to each energy level and sublevel in the configuration
You will determine how to write electron configuration and orbital notation for atoms and ions.

28. Write the orbital notation for the following atoms:
Examples
Write the orbital notation for the following atoms:
Sulfur
Silicon
Magnesium
You will determine how to write electron configuration and orbital notation for atoms and ions.

29. Electron Configurations
Electron Configuration and Orbital Notation change for elements after the first 20.
This is because instead of going in order of each energy level and sublevel, we jump from the 4s to 3d
An example of an electron configuration with this: Se - 1s22s22p63s23p64s23d104p4
Notice the jump from 4s to 3d then back to 4p
You will determine how to write electron configuration and orbital notation for atoms and ions.

30. Ga – 1s22s22p63s23p64s23d104p1 Br - 1s22s22p63s23p64s23d104p5
Examples
Give the electron configuration for gallium (Ga), bromine (Br) and hafnium (Hf).
Ga – 1s22s22p63s23p64s23d104p1
Br - 1s22s22p63s23p64s23d104p5
Hf - 1s22s22p63s23p64s23d104p65s24d105p66s24f145d2
You will determine how to write electron configuration and orbital notation for atoms and ions.

31. Try on your own
Give the electron configurations for the following elements:
tin (Sn)
lead (Pb)
polonium (Po)
iodine (I)
tin (Sn) - 1s22s22p63s23p64s23d104p65s24d105p2
pollonium (Po) –
1s22s22p63s23p64s23d104p65s24d105p66s24 f145d106p4
lead (Pb) -
1s22s22p63s23p64s23d104p65s24d105p66s24 f145d106p2
iodine (I) - 1s22s22p63s23p64s23d104p65s24d105p5
You will determine how to write electron configuration and orbital notation for atoms and ions.

32. Orbital Notation
Pick one atom from the last set of problems and write its orbital notation
You will determine how to write electron configuration and orbital notation for atoms and ions.

33. Summarize how you feel …
You will:
Determine the energy levels, sublevels and orbitals of electrons in an atom.
Determine how to write electron configuration and orbital notation for atoms and ions.