1. The Bohr Model 2:
Quantum Mechanics

2. Explain the historical development of the Quantum Mechanical Model of the atom.
Describe the quantum arrangement of electrons in an atom.
Include: energy level, shape, and orbital.
Additional KEY Terms
Principal quantum number (n)

3. de Broglie (1924) – developed an equation that predicts wave qualities for all matter.
If waves of light could contain photon-particles, could matter have wave properties?
Suggests orbits are fixed because electrons (as a wave) could only move as strict
standing wavelength

4. The famous “double-slit” experiment proved the “wave-particle duality” of matter (click the TV link below)

5. Think - trying to catch a frog in the dark with a flashlight…
Problems:
World is 3-dimensional
Bohr’s math failed to explain all spectra
Matter also has wave properties
Heisenberg (1925) - it is impossible to know precisely the velocity and position of a particle at the same time – Heisenberg Uncertainty Principle
Think - trying to catch a frog in the dark with a flashlight…

6. Schrödinger (1926) – developed a wave equation that describes the energies and behaviour of subatomic particles.
Determines the probability of finding an electron in a 3-D volume of space around the nucleus.
At this point, scientists couldn’t really figure matter out experimentally, so they turned to math and computers…

7. Each energy level's boundary is the area of electron location 90% of the time

8. principle quantum number (n)
Bohr’s orbits are now called:
principle quantum number (n)
The (n) number indirectly describes the size and energy requirements of an orbit

9. The probable location of every electron is now described by a set of 4 quantum numbers:
principal (n)
distance from the nucleus
2. orbital angular momentum (l)
shape of orbital
3. magnetic (m)
orientation in 3D space
4. spin angular momentum (s)
spin of the election

10. s p d f There are four shapes appearing in this order:
Principle quantum numbers (n) contain many places of probable electron location – shapes (l)
There are four shapes appearing in this order:
s p d f
Each shape (l) can be made of multiple orbitals (m) that occupy the axes of 3D space (x, y, z)
Each orbital holds two spinning electrons (s)

11. Like stadium seating, the further from the stage the more “sections” of seating
NUCLEUS
n = 1 s
n = 2 s p
n = 3 s p d
Notice: number of shapes (l) equal the principal quantum number (n) for that level

12. “s” shape (sphere) – 1 orbital (m)
Only one “way” to place a sphere in 3D space

13. “p” shape (dumbbell) – 3 orbitals (m)
Three orientations for placing a dumbbell in 3D space

14. “d” shape (cloverleaf) – 5 orbital orientations (m)
“f” shape (indeterminate) – 7 orbital orientations (m)

15. Remember – each orbital (m) holds two spinning electrons (s)
Principal Level (n)
Shapes
(l)
Total Orbitals 1 s
1s = 1 2
s,p
1s+3p = 4 3
s,p,d
1s+3p+5d = 9 4
s,p,d,f
1s+3p+5d+7f = 16 n
n shapes
n2 orbitals
Remember – each orbital (m) holds two spinning electrons (s)

16. n = 3 1s 2s 2p 3s 3p 3d
n = 2
n = 1
OLD way
NEW way

17. CAN YOU / HAVE YOU?
Explain the historical development of the Quantum Mechanical Model of the atom.
Describe the quantum arrangement of electrons in an atom.
Include: energy level, shape, and orbital.
Additional KEY Terms
Principal quantum number (n)