Bohr Model vs. Quantum Theory

Wave/Particle Paradox Light sometimes acts as a particle and sometimes acts as a wave. Thomas Young noticed that when electrons are forced through a narrow slit, a pattern of wave interference emerged. He was familiar with Rutherford’s Thompson’s experiment that showed electrons are particles and needed to reconcile the two points of view.

Double Slit Experiment What it would look like if a wave went through two slits…. What it would look like if particles go through two slits…. What it looks like when electrons go through two slits…

Wave/Particle Paradox This reconciliation led to the development of the Quantum Mechanical Model of the atom. The Quantum Mechanical Model is based on complex mathematical equations developed by Erwin Schrodinger that describe the wave nature of the atom and the locations of the electrons.

These are the equations that determine where electrons can “live” (credit to Jack Helgeson for writing the equations for Ms. LaPlante years ago)

Bohr (left side of table) Nuclear model (model says atoms have a nucleus) Electrons orbit the nucleus like planets around the sun. Electrons are treated like particles. Electrons’ energy is quantized.

Quantum Theory (right side of table) Nuclear model Electrons occupy orbitals, which are probability spaces described by mathematical models. Electrons are treated like waves. Electrons’ energy is quantized.

When atom is not energized Bohr Model When atom is not energized When atom is energized

When atom is not energized Quantum Model When atom is not energized When atom is energized

Some more pictures of orbitals (from the website http://winter. group

Quantum Theory (based partly on Heisenberg’s Uncertainty Principle) The position and the momentum of a moving object cannot simultaneously be measured and known exactly There is an inherent limitation to knowing both where a particle is at a particular moment and how it is moving in order to predict where it will be in the future

Quantum Theory An electron is in an orbital – probability space where an electron can be found a certain percentage of the time as defined by Shrodinger’s equations An orbital can hold 2 electrons (this means the bigger the energy level, the more orbitals it has) (add this to your notes): s = 1 orbital, p = 3 orbitals, d = 5 orbitals, f = 7 orbitals