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### The Quantum Mechanical Model

Warm Up 9/20

- Draw the Bohr Model for Aluminum
- What is the difference between a hypothesis and a theory?

Chemistry

Bohr’s Model

- Bohr energized hydrogen electrons

(1 e- per atom)

- Energized electrons jumped certain distances from the nucleus

Bohr’s Model

- Bohr saw 4 colors
- Each color has a specific wavelength

Bohr’s Model

- Each wavelength corresponds to a distance from the nucleus
- These distances are called “shells” or “energy levels”

Bohr was wrong

- While Bohr’s theory worked for hydrogen, it could not be applied to any other element because they all have more than one electron

Werner Heisenberg

- 1927, Germany
- Heisenberg Uncertainty Principle = It is impossible to determine simultaneously both position and velocity off an electron or any other particle

Heisenberg’s Uncertainty Principle

- It’s impossible to determine where any one electron is at any point in time.
- Scientists talk about probabilities of electrons locations (electronic cloud).

Erwin Schrödinger

- Physicist from Austria
- Late 1920’s
- Wrote an equation to describe the probable location of an electron

Quantum Mechanical Model

- Current Electron Theory
- Created by Schrödinger
- Involves Quantum Numbers
- Can be shown using Electron Configurations (ex: 1s22s22p5)

Quantum Numbers

- Each electron is located in an energy level (n), which is within a sub-level with a shape (l).

Quantum Numbers

- A sub-level is made of orbitals. Different electrons within the same sub-level will have a different orientation (ml) depending on the orbitals orientation within the sub-level.
- Each orbital can have 2 electrons max, but they have opposite spin (ms)

Quantum Mechanical Model

- Electrons are arranged into Energy Levels or Shells (1, 2, 3, 4, …).
- The “Principal Quantum Number” (symbolized by n) indicates the main energy level occupied by the electron

Quantum Mechanical Model

- Energy Levels contain sub-levels (s, p, d, f)
- The “Azimuthal or Angular Momentum Quantum Number” (symbolized by l) indicates the shape of the sub-level

Quantum Numbers

- Magnetic Quantum Number (ml) indicates the orientation of an orbital around the nucleus
- For example, the sub-level “p” is composed of 3 different orbitals (px, py, and pz)
- Scientists use the values -1, 0, and +1 to tell the orbitals apart.

Practice with Magnetic Quantum Numbers

- What would be the magnetic quantum number used for the s sub-level?
- What would be the magnetic quantum numbers used for the d sub-level?

Spin Quantum Number,ms

- A maximum of 2 electrons can fit into each orbital. BUT electrons don’t like each other (repel)
- 2 spins = +1/2 (up) and -1/2 (down)

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