Electromagnetic Spectrum Section 1 The Development of a New Atomic Model Chapter 4

Wavelength and Frequency Section 1 The Development of a New Atomic Model Chapter 4

Light as a wave Wavelength and frequency related by: c = λv

Photoelectric Effect Section 1 The Development of a New Atomic Model Chapter 4

Light as a particle Photon Packet of energy E = hv Can be absorbed and emitted by atoms Light has dual wave/particle nature

Hydrogen’s Line-Emission Spectrum Section 1 The Development of a New Atomic Model Chapter 4

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

Photon Emission and Absorption Section 1 The Development of a New Atomic Model Chapter 4

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

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

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

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.

Relative Energies of Orbitals Chapter 4