Download Models of the Atom

Chapter 4
Section 1 The Development of a New
Atomic Model
Electromagnetic Spectrum
Chapter 4
Section 1 The Development of a New
Atomic Model
Wavelength and
Frequency
Light as a wave
• Wavelength and frequency related by:
• c = λv
Chapter 4
Section 1 The Development of a New
Atomic Model
Photoelectric Effect
Light as a particle
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•
•
•
Photon
Packet of energy
E = hv
Can be absorbed and emitted by atoms
• Light has dual wave/particle nature
Chapter 4
Section 1 The Development of a New
Atomic Model
Hydrogen’s Line-Emission
Spectrum
Bohr model of hydrogen atom
Bohr Model of Atom
• Explained hydrogen’s line emission spectrum – bands of
light emitted by an atom
• e- can only exist at fixed energy levels
• Absorption – e- absorbs a photon and jumps to a higher
energy level
• Emission – e- falls to a lower energy level and emits a
photon
• Ground state – all e- in lowest possible energy levels
• Excited state – at least one e- has absorbed a photon
and jumped to a higher energy level
Chapter 4
Section 1 The Development of a New
Atomic Model
Photon Emission and
Absorption
Determining energy between levels
• Measure the wavelength of light emitted
• Calculate frequency using c = λv
• Calculate energy using E = hv
Bohr model of hydrogen atom
Limitations of Bohr Model
Limitations of Bohr Model
• Explained the line emission spectrum of H
Limitations of Bohr Model
• Explained the line emission spectrum of H
• Did not explain
Limitations of Bohr Model
• Explained the line emission spectrum of H
• Did not explain
– Line emission spectrum of other atoms
Limitations of Bohr Model
• Explained the line emission spectrum of H
• Did not explain
– Line emission spectrum of other atoms
– Chemical behavior of atoms
Limitations of Bohr Model
• Explained the line emission spectrum of H
• Did not explain
– Line emission spectrum of other atoms
– Chemical behavior of atoms
– Why only certain energy levels existed
De Broglie’s Hypothesis
De Broglie’s Hypothesis
• Electrons can act as waves
De Broglie’s Hypothesis
• Electrons can act as waves
– confined to space around nucleus
De Broglie’s Hypothesis
• Electrons can act as waves
– confined to space around nucleus
– set up 3D standing waves around nucleus
De Broglie’s Hypothesis
• Electrons can act as waves
– confined to space around nucleus
– set up 3D standing waves around nucleus
– Only specific frequencies are allowed
De Broglie’s Hypothesis
• Electrons can act as waves
– confined to space around nucleus
– set up 3D standing waves around nucleus
– Only specific frequencies are allowed
– And, hence, only certain energy levels
Heisenberg Uncertainty Principle
• Impossible to know both the position and
velocity of an electron at the same time.
• Electrons do not follow fixed paths.
• Can only identify a region where an
electron might exist.
Schrodinger’s Wave Equation
Schrodinger’s Wave Equation
•
Describes what those regions look like.
– called orbitals
Schrodinger’s Wave Equation
•
Describes what those regions look like.
– called orbitals.
•
Solution to equation: 3 quantum numbers
Schrodinger’s Wave Equation
•
Describes what those regions look like.
– called orbitals.
•
Solution to equation: 3 quantum numbers
1. Main energy level
Schrodinger’s Wave Equation
•
Describes what those regions look like.
– called orbitals.
•
Solution to equation: 3 quantum numbers
1. Main energy level
2. Shape of orbital
Schrodinger’s Wave Equation
•
Describes what those regions look like.
– called orbitals.
•
Solution to equation: 3 quantum numbers
1. Main energy level
2. Shape of orbital
3. Orientation of orbital
Schrodinger’s Wave Equation
•
Describes what those regions look like.
– called orbitals.
•
Solution to equation: 3 quantum numbers
1. Main energy level
2. Shape of orbital
3. Orientation of orbital
•
Quantum numbers give the address of
electrons in the atom.
Quantum model of atom
Energy levels in the atom are like
an upside down pyramid building.
Chapter 4
Relative Energies of Orbitals