Bohr Model, Energy Level & DeBroglie Flashcards
What causes chemical reactions?
Changes in electron structure
What causes change in electron structure?
Interactions with light and/or electromagnetic radiation
What is electromagnetic radiation?
Any kind of radiation from the electromagnetic spectrum (Gamma, X-Ray, infra-red etc)
How can light be used to investigate electron structure?
1) You can add electrical energy to a vaporized sample (Investigate lights) (Emission spectra)
2) Shine full spectrum of light at a vaporized sample (Look for absorption of light) (Absorbtion Spectra)
Solar absorption spectrum
- Dark lines show where light absorbed
- Frequencies absorbed characteristics of certain elements
- Identifies elements in suns atmosphere
What is emission spectra?
Adding energy to atoms resulting in an emission of light
What is absorption spectra?
Shining light through a vaporised element, resulting in absorption of some wavelengths of light
Electron excitation
When a bound electron is transferred to a more energetic energy state
Electron relaxation
When an electron in an excited state drops to a lower energy state
Photon absorbtion
When a photon loses it’s energy to an atomic electron which is then emitted from an atom
Photon emission
When an electron drops to a lower energy state the atom emits a photon
What is an electron energy level?
Reqions around the nucleus of an atom where electrons may be found
Whats a ground sate for an atom?
Its the lowest energy state for an atom, electrons can’t move to a lower orbital
Absorption and emission spectra
- Spectral lines indicate change in energy values for electron energies in an atom
- Higher energy photons correspond ( Shorter wavelengths)
What is lyman series
Transitions from higher energy orbits to the lowest energy orbit available (visible series; Ultra-violet)
What is paschen series?
Transitions from higher energy orbits to the orbit n=3 (Infra-red)
What is balmer series
Transitions from higher energy orbits to the orbit n=2 (visible series)
What is pfund series?
Transitions from higher energy orbits to the orbits n=5
What is brackett series?
Transitions from higher energy orbits to the orbit n=4
Rydbergs formula
Calculates the wavelength of a spectral line in many chemical elements
Bohr’s model
- atoms have certain energy levels
- Atom doesn’t radiate energy while its in a stationary phase
- Atom changes to another stationary state only by absorbing or emitting a photon
- Energy of a photon equals the difference in the energies of the two states
What are the limitations of Bohr’s model?
- Fails for multi electron systems; only works for single electron systems
- No explanation for why there are allowed orbits
What is Z?
Charge of the nucleus, +1 for Hydrogen
What does the energy lost by an atom correspond to?
Corresponds to the energy of a released photon (conservation of energy)
Conservation of energy
- Applies to both atom and photon
- States energy cannot be created nor destroyed; only converted from one energy form to another
What was DeBroglies hypothesis?
- Proposed if energy is particle like, matter is wave like
- Electrons only have certain allowable frequencies if they have wave like motion in orbits at fixed distances from nucleus
- His equation can find the wavelength of any particle mass
What is P?
P= momentum which is inversely proportional to wavelength
Whats the wave concept for electrons?
- Constructive & destructive inference
- Allowed orbits = constructive inference
- Forbidden orbits will self destruct
- Allowed orbits correspond to complete wavelengths
What are the consequences of electron wave?
- Location of wave like particle is imprecise
- Heisenberg uncertainty principle; cannot know both precision and momentum with certainty (If one is known accurately the other is imprecisely)
Uncertainty principle
Single plane wave - will have precise energy and momentum; position of electron is infinite
Wave packett - position of electron is localized from adding different waves; energy and momentum now imprecise
