Warm Up9/20 Draw the Bohr Model for Aluminum What is the difference between a hypothesis and a theory?

The Quantum Mechanical Model 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: 1s 2 2s 2 2p 5 )

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 (m l ) depending on the orbitals orientation within the sub-level. Each orbital can have 2 electrons max, but they have opposite spin (m s )

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

NRG Sub-level “s” Azimuthal Quantum Number 0 “s” sub-level l = 0 Sphere shape Contains 2 e- One Orbital

NRG Sub-level “p” Azimuthal Quantum Number 1 “p” sub-level l = 1 Contains maximum 6 e- 3 orbitals

NRG Sub-level “d” Azimuthal Quantum Number 2 “d” sub-level l = 2 Maximum 10 e- 5 orbitals

NRG Sub-level “f” Azimuthal Quantum Number 3 “f” sub-level l= 3 Maximum 14 e- 7 orbitals

Quantum Numbers Magnetic Quantum Number (m l ) indicates the orientation of an orbital around the nucleus For example, the sub- level “p” is composed of 3 different orbitals (p x, p y, and p z ) 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, m s 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)