Unit 3 - Atomic Theory

Electromagnetic Wave

Interacting, changing electric and magnetic field that travel outwards from source and perpendicular to each other

Switching magnetic poles creates 

Waves

Thermal Radiation

Object at any temperature emitting electromagnetic radiation

Blackbody Radiation

Object that perfectly absorbs all light and doesn’t reflect any light that reaches it, emitting a continuous spectrum, determined only by temperature of blackbody

Wien’s Law

Peak of distribution shifts to shorter wavelengths

Stefan’s Law

Total energy emitted by object increases with temperature

Prior to 19th Century Physics

• Universe was divisible into particles and waves

• Smooth on scales

• Deterministic

Rayleigh-Jeans Law

Classical model of radiation that assumes object can emit any amount of radiation at any wavelength

UV Catatrosphe

Disagreement between data and equation at short wavelength assuming infinite energy as wavelength approaches 0

Assumptions about Blackbody

1. Each frequency, amount of energy has certain discrete values

2. Thermal oscillators emit/absorb energy when making transition from a quantum state to another

Photoelectric Effect

Emission of electron from surface when light hits 

Max KE is independent of incident light but

Frequency must reach threshold

Stopping Potential

Minimum negative PE to be applied to collector electrode to stop flow of all photoelectrons

Electron Volt

Energy acquires when electron undergoes change in PE of 1 Volt

Dalton Model

• All matter composed of atoms that’s indestructible

• All atoms of the same element are the same 

• Chemical reactions happen when atoms rearrange with specific ratio

• Atoms have no structure

Fundamental Unit of Charge

Magnitude of electric charge carried by a single proton or electron

Rutherford’s Model

Positive core surrounded by electrons circulating like planets using gold foil experiment

Rutherford’s Cons

• Electron orbiting nucleus should emit EM waves with a continuous rainbow spectrum

• Constant emission of EM waves means electrons should be losing PE and spiral to the centre

Bohr’s Model Assumption

• Each atom has discrete states, spectrum

• Ground state is stable 

• Emission spectra produced by collisions

• Every element has unique different absorption wavelength with different colours

Negative energy in levels means

It takes energy to leave nucleus because electron is bounded

Hydrogen Like Atoms

All but 1 electron has been removed

Lyman Series

Begins at n=1

Balmer Series

Begins at n = 2

Paschen Series

Begins at n = 3

Bracket Series

Begins at n = 4

Binding Energy

Energy to remove electron from orbit

Ionization Energy

Energy needed to make an ion by removing ground state electron

Absorption Spectrum

Obtained by passing light through gas/dilute solution of element which it absorbs colour it radiates

Discrete Line Spectrum

Low pressure gas is subjected to electric discharge and electron transition

Wave Particle Dualityr

Electrons will be like waves or particles but never at the same time

Heisenberg’s Uncertainty Principle

Acts of measurement disturbs the system and there are limits to how precisely p and position of a particle can be measured at the same time, applied only to pairs of quantities that directly depend on each other

A particle in a box/bounded will have

Quantized energy levels

Electrons are wave packet that interaction with

Many waves constructively interfering in a spot and destructively everywhere else

Time Independent Schrodinger Equation in 1D

• Phi(s) continues everywhere for when x = infinity

• Phi(x) is normalized (it’s somewhere in the world)

In finite box, particles can 

Bounce out of the wall through tunneling and electron can leave

Quantum Tunneling

Quantum mechanical phenomenon where particle pass through PE barrier even if its doesn’t have enough energy to overcome classically

n

Principal quantum number

l

Orbital quantum number 0 < l < n-1

m_l

Magnetic quantum number, -l < m_l < l

Number of possible electron state in subshell is

2(2l+1)

Exclusion Principle

No 2 electron in the same atom can be in the same quantum state or numbers

Subshell

Unique combination of n and l

Nucleon

General name for both proton and neutron

Z

Number of protons

N

Number of neutrons

A

Z + N

Isotopes have the same

Chemical but not physical properties

Isobars

Same A but different Z and N

Isomers

Identical nuclei with same A and Z but different energy states

1st Nucleus Model

Atom of atomic number Z and atomic mass has a nucleus with A protons and A - Z electrons 

1st Nucleus Model Con

No evidence of right force to bond the protons and electrons in nucleus

Density of nucleus is

Constant and therefore incompressible

Line of Stability

Stable nuclei on the graph, nuclei far from stability is radioactive

Nuclear Force

Force between proton and neutron contact free, strong force binding them to nuclei based on mass

Positive Nuclear Force

Repulsive

Negative Nuclear Force

Attractive but when it surpasses nucleus, force is weakened

Binding Energy

Difference between total energy of proton and neutrons and total energy of nucleus, mass becomes the energy that bonds them