Chapter 4 Sections 1 and 2

Chapter 4 Section 1

The Development of a New Atomic Model

Bohr Model of Hydrogen Atom (continued)

• When an electron falls to a lower energy level, a photon is emitted, and the process is called emission.
• Energy must be added to an atom in order to move an electron from a lower energy level to a higher energy level. This process is called absorption.

Photon Emission and Absorption

• E-photon = E-2( orbit 2) subtracted by E-1 is the Absorption
• E-photon = E-1 - E-3 is the Emission

Chapter 4 Section 2

The Quantum Model of the Atom

Electron waves

• French scientist Lonis de Broglie suggested that electrons be considered waves confined to the space around an atomic nucleus.
• It followed that the electron waves could exist only at specific frequencies.
• According to the relationship E=hv, these frequencies corresponded to specific energies - the quantized energies of Bohr's orbits.
• Electrons, like light waves, can be bent, or diffracted.
• Diffraction refers to the bending of a wave as it passes by the edge of an object or through a small a opening.
• Electron beams, like waves, can interfere with each other.
• Interference occurs when waves overlap.

The Heisenberg Uncertainty Principle

• German physicist Werner Heisenberg proposed that any attempt to locate a specific electron with a photon knocks the electron off its course,
• The Heisenburg Uncertainty principle states that it is impossible to determine simultaneously both the position and velocity of an electron or any other particle.

The Schodinger Wave Equation

• In 1926, Austrian physicist Erwin Schodinger developed an equation that treated electrons in atoms as waves.
• Together with Heisenberg uncertainty principle, the Schodinger wave equation laid in the foundation for modern quantum theory.
• Quantum Theory describes mathematically the wave properties of electrons and other very small particles.