2 LightThe idea for the the quantum mechanical model grew out of the study of lightLight consists of wavesThe amplitude of a a wave is the height from zero to crestWavelength (λ) is the distance between crestsFrequency (ν) is the number of wave cycles that pass a given point per unit of timeFrequency is measuredin hertz (Hz)
3 Lightc= λνc is a constant, equal to x 108 m/s, so frequency and wavelength are inversly proportional
5 Atomic SpectraAtoms can absorb energy that raises electrons into higher energy levels.The electrons then lose the energy by emitting light when electrons return to their lower energy level.The light emitted by electrons only contains certain wavelengths of light.Each frequency corresponds to a specific colorEach element emits a unique atomic emission spectrum
7 How it WorksAn electron has a lowest possible energy called it’s ground state.For hydrogen, its ground state is n=1Absorbing energy can excite the electron to n=2,3,4,5 or 6A quantum of energy in the form of light is emitted when an electron drops back to a lower energy levelThe light emitted by an electron transition from higher to lower is derectly proportional to the energy change in the electron, therefore each transition produces a line of a specific frequency in the spectrum
9 Quantum Mechanics Light has a dual wave/particle nature Particles of light are called photonsExperiments showed that electrons also behaved like particles and wavesThis wave like nature is used in electron microscopes since electrons have a much smaller wavelength than visible lightQuantum mechanics describes the motion of subatomic particles and atoms as waves
10 Heisenburg Uncertainty Principle It is impossible to know exactly both the velocity and position of a particle at the same time
11 Tying it TogetherThe discovery of matter waves paved the way for Schrodinger’s quantum mechanical atom model. His theories include the wavelike motion of matter and the uncertainty principle.