Bohr Model (Shell Model)

1. Bohr Model (Shell Model) • Evidence suggested electrons occupied specific energy levels (shells) while “orbiting” around nucleus • Essentially based on Coulomb’s Law k = coulomb’s constant q = object with a charge r = radius (distance between the 2 charged particles) • Was used to help explain why electrons didn’t come “crashing” into the nucleus (since opposites attract) • Attractive force between nucleus and electron is balanced by electron’s centrifugal force • The Bohr model makes great predictions BUT there’s a couple things about electrons we discovered: • Uncertainty • Electron spin

2. Uncertainty: - Heisenberg Uncertainty Principle • We can never know BOTH the: • Location of an electron • Momentum of an electron • Because of this, we realized that electrons live in these “clouds” of probability • Don’t follow specific orbits • Orbital • Where electrons spend their time • Electrons have a Spin • Clockwise or counter-clockwise magnetic spin • As a result of this electron spin: • Only two (max) electrons can exist in an orbital • This forced us to modify our “shell” (Bohr) model in order to better align with the evidence of reality • Quantum mechanical model of the atom • Computers allowed us to complete complex equations and software to predict how atoms are going to interact

3. Orbitals s orbital d orbitals ALL of these orbitals simply represent “clouds” of probability where electrons sit p orbitals f orbitals

4. Quantum Numbers • Size (n) • Size of the orbital • As n gets larger then the area in which the electron occupies gets larger as well • These numbers allow us to predict WHERE electrons are most likely to be found which allows us to predict: • What an atom looks like • How atoms are going to interact • Shape (l) • Shape of the orbital • Can be either an s, p, d, f • Orientation (ml) • Tells us the number of orientations the orbitals can have • s 1 orientation • p 3 orientations • d 5 orientations • f 7 orientations • Spin (ms) • Clockwise (+1/2) • Counter-clockwise (-1/2) • Dictates that only 2 electrons can exist in an orbital

5. Electron Configuration • Distribution of electrons • Where the electrons are found in atoms OR in ions • Ionization energy • Amount of energy it takes to remove an electron • Can be quantified using Coulomb’s Law • Multielectron atoms or ions • Shells, subshells, and orbitals similar ionization energy Nucleus Core electrons Valence electrons shield

6. Atomic number hydrogen Each box represents and orbital Each arrow represents an electron

7. Atomic number helium Each box represents and orbital Each arrow represents an electron

8. Atomic number lithium Each box represents and orbital Each arrow represents an electron

9. Atomic number beryllium Each box represents and orbital Each arrow represents an electron

10. Atomic number boron Each box represents and orbital Each arrow represents an electron

11. Atomic number carbon Each box represents and orbital Each arrow represents an electron

12. Atomic number nitrogen Each box represents and orbital Each arrow represents an electron

13. Atomic number oxygen Each box represents and orbital Each arrow represents an electron

14. Atomic number fluorine Each box represents and orbital Each arrow represents an electron

15. Atomic number neon Each box represents and orbital Each arrow represents an electron

16. Atomic number sodium Each box represents and orbital Each arrow represents an electron

17. Atomic number magnesium Each box represents and orbital Each arrow represents an electron

18. Periodicity 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p hydrogen 1s1

19. Periodicity 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p boron 1s22s22p1

20. Periodicity 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p neon 1s22s22p6

21. Periodicity 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p sodium 1s22s22p63s1

22. Periodicity 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 6s 6p 6d 7s 7p chromium 1s22s22p63s23p64s23d4 Same thing [Ar]4s23d4