Chapter 4 Section 1 The Development of a
- Slides: 34
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 • • 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 3 D standing waves around nucleus
De Broglie’s Hypothesis • Electrons can act as waves – confined to space around nucleus – set up 3 D 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 3 D 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