Chapter 7 - Quantum Theory and Atomic Structure
conclusion from Heisenberg Uncertainty Principle
The more accurately we know a particle's position, the less accurately we can determine its momentum - and vice versa
d orbital
clover shaped
f orbital
daisy shaped
for a one e- hydrogen atom, orbitals w. the same n are . . .
degenerate or have the same energy
Quantum Theory of Energy
explained blackbody radiation by assuming that energy comes in packets called quanta (singular: quantum) energy is quantized: Atoms can gain or lose energy by absorbing or emitting energy only in whole quanta
ψ^2 The square of the wave function
gives the electron density, or probability of where an electron is likely to be found any given time
relationship between wavelength and frequency
inversely related
s orbital
spherical
amplitude
the maximum height of a wave
frequency v
the number of waves passing a fixed point each second (sec-1 or Hz)
orbital
the volume or space where an e- is likely to be found
Limitations of Bohr's Model
• Only works for hydrogen atoms • Treats electrons solely as particles •Does not explain why the electron does not continuously emit energy and fall into the nucleus
Quantum Mechanics
describes the energies and arrangements of e- mathematically - describes the size (distance from nucleus) and overall orbital energy level
p orbital
dumbbell
Electromagnetic radiation
carries energy through space (aka radiant energy)
Three observed properties associated with how atoms interact w/ electromagnetic radiation are NOT explainable by treating light as a wave
1) blackbody radiation: emission of light from hot objects 2) the photoelectric effect: emission of e- from metal surfaces on which light is shined 3) emission spectra: emission of light from electronically excited gas atoms
e- (1) emitted and (2) absorbed
1. ni > nf ΔE<0 2. ni < nf ΔE>0
Electromagnetic Radiation (EMR) is quantized properties???
EMR is both a wave and a stream of particles (photons) EMR has dual nature properties: •Particle-like •Wave-like
The Photoelectric Effect
Einstein explained this with quanta Each metal has a different energy at which it ejects electrons. At lower energy, electrons are not emitted. Light consists of particles (photons) each with a discrete amount of energy
ground state excited state
Electrons in their lowest possible energy levels Any higher energy state (further from the nucleus)
Heisenberg Uncertainty Principle
It's impossible to know both the exact position (x) and exact momentum (mv) of an e- at any given time
Bohr's Model
Niels Bohr adopted Planck's assumption and explained these phenomena in terms of a new model of the atom: Now called "quantum theory" 1. Electrons can only exist in certain discrete orbits - The energy of each orbit is QUANTIZED (can have only certain values of energy) 2. An electron in a permitted orbit is in an "allowed state" -Does not radiate energy 3. Energy is absorbed or emitted by the electron as a photon (E = hν) but only as the electron changes from one allowed energy state to another
wavelength 𝞴
The distance between corresponding points on adjacent waves