Quantum Mechanics
Electromagnetic Radiation
Definitions of new words:
Light: electromagnetic radiation composted of oscillating electric and magnetic fields
Wave: characterized by its amplitude and wavelength
Amplitude: vertical height of a crest
Wavelength: distance between adjacent crests (meters)
nu: number of wave crests that passes through a single point per second (hertz)
Additional notes:
- Speed of light (c) is 3.00 x 10^8 m/s
- Lambda is expressed in meters
- Nu is expressed in reciprocal seconds
- Gamma rays, X-rays, UV radiation, Infared, Microwaves, Radio waves: longest wavelengths
The Wave Nature of Light
Definitions of new words:
Quantum mechanics: study of matter and light on the atomic and subatomic scale
Blackbody radiation: spectrum of light that is emitted by heating a solid object
A quantum of energy: smallest quantity of energy that can be emitted or absorbed
Photoelectric effect: an effect observed when metals are in the presence of light they can emit electrons
Photon of light: packet of energy
Additional notes:
Double Split Experiment: diffraction of light through two slits produces interference pattern
- When waves interact, they can cancel each other out or increase amplitude
Types of Interferences
1) Constructive: waves are in sync
2) Destructive: waves cancel each other out
Maxwell's electromagnetic theory
hypothesized oscillating electric and magnetic fields of light traveling at the speed of light
Photon of light equation: E=hv
- h is called Planck's constant: 6.626 x 10^-34 Js
! Energy of a photon can also be expressed in terms of wavelength by using speed of light equation
- Radian energy is emitted and absorbed in discrete quantities
- If an photon is below threshold, electrons will not be emitted from the metal because the photon is not strong enough to overcome the binding energy
- If the photon is above threshold, the additional energy is transferred to the electron via kinetic energy
--->Ekinetic=Eproton- (threshold)
Atomic Spectroscopy
Definitions of new words:
Atomic spectroscopy: study of electromagnetic radiation that is absorbed or emitted by atoms
Emission spectrum:
Additional notes:
- Atoms can absorb energy in form of heat, light, or electricity
- Different elements emit their own unique emission spectrum
- An electron in a stationary state does not emit radiation
- Radiation is emitted or absorbed only when electrons transition between orbits
Equation for energy emitted from an atom
E=-Rh (1/nfinal2- 1/initial2)
Rh=2.18x10^-18
1J=kg m^2/s^2
Heisenberg Uncertainty Principle
Definitions of new words:
Complementary properties: the more you know about one the less you know about the other
Heisenberg Uncertainty Principle: you cannot know for certainty of both the velocity and postion of an electron
Additional notes:
Steel Chamber experiment
- Contents: radioactive material, cat, poison, geiger counter, hammer
- If Geiger detects poison, the hammer will kill cat
Louis De Brogile
- Suggests that particles must be transported by a wave and that light can behave as a wave and a particle
- Solved the paradox of light; acting as both a wave and a particle
- This introduces complementary properties: the more you know about one the less you know about the other
Quantum Mechanics
Definitions of new words:
Shell: any orbital with same value "n" and a subshell are orbitals with the same value "n" and "1"
S orbital: lowest energy orbital, symmetrical, L=0, ML=0
P orbital: three orientations (-1, 0, 1) on XYZ plane
D orbital: 5 orientations (DXZ, DYZ, DXY, DX^2-Y^2, DZ^2)
Additional notes:
- Heisenberg's uncertainty principle states that you cannot know what certainty both the position and the velocity of an electron
- Each orbital can hold a maximum of TWO electrons
Quantum numbers: first 3 describe orbital while the 4th describes orientation
1) Principal quantum number (n): corresponds to size and energy of the orbital and n is an integer > (or equal to) 1
- Describes energy level in which the electron is located
- "City"
- Represents N in bohr equation
2) Angular momentum number
- Denotes shape of the orbital and is calculated by I=0 to n-1 including all integers in between
- "Zipcode"
3) Magnetic momentum quantum (m1)
- Determines orientation in space of the orbital, so this denotes where on the XYZ plane this orbital lies opon
- m1=-1...0...+1
- "Street Address"
4) Spin quantum number (ms)
- Specifies the orientation of the electron in the orbital, which an electron can be spin up +1/2 or spin down -1/2