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All objects emit

### temperature

What type of radiation a body will emit depends on its

### higher energy EM wave emitted

Higher temperature =

### blackbody

An ideal system that absorbs all incoming radiation is called a

emitted by blackbody, emits radiation only based on its temperature

### Max Planck

Developed a formula that explained blackbody radiation

### resonators

Explained that black body radiation was due to submicroscopic electric oscillators called

### quantized energy

Planck assumed that these resonators could only absorb and give off certain amounts of energy - called

E = nhf

### n

is the quantum number (energy level, usually 1)

### h

is planck's constant: 6.63x10-34 Js

### f

is the frequency of the light wave

### electronvolt (eV) - 1eV

Another energy unit used in quantum mechanics is the ____ = 1.60x10-19J

### quantized

Einstein proposed that all electromagnetic waves are _____ - meaning they are bundles of energy (photons)

### photoelectric effect

Einstein won the 1921 Noble Prize for this explanation of the

### force

In order to eject electrons, the electron must overcome the_____ holding it to the atom

### The work function

____is the minimum amount of energy required to help the electron escape from the atoms of the metal (E = hfo) where fo is the threshold frequency for the metal

### maximum kinetic energy

The electrons ejected have a _____that can be found by the following equation: KEe = hf - work function

### ejected

The greater the frequency of light, the greater the KE of the electrons____

### instantaneously

The electrons are ejected almost___

### metal's threshold frequency

The photoelectric effect will not be observed if the frequency of light shone on a metal is not at least at that ____

### energy (frequency)

The amount of light shone on the metal doesn't matter, only the____ of the light matters

### will not

A more intense light source ___ generate higher KE electrons

### electron

Each photon affects one____

### Arthur Compton

____ realized that if light behaved like a particle, then a collision between an electron and a photon should be similar to two balls colliding

### momentum & energy

Photons should carry ____ as well as ____

### Compton Shift -

increase in wavelength of light as it strikes an electron

### X-rays and gamma rays

Compton shift is difficult o observe with visible light, easier to see in

### Problems with Rutherford's Model

If electrons orbit the nucleus, then why don't they undergo centripetal acceleration
; Orbiting electrons should produce magnetic fields according to Maxwell's Equations - this would cause them to loose energy
; A lost in energy would cause the electron orbit to decrease - the atom would collapse

### light

When a pure gas fills a tube and a potential difference is applied across the tube, the gas will give off ___

### unique emission and absorption spectrum

Each gas has a ____ & ____

### Emission spectrum -

bright lines that correspond to the wavelength of light given off by a gas

### Absorption spectrum -

white light is shone on the gas, the spectrum is a band of dark lines indicating what wavelengths of light were absorbed by the gas

### spectrums

All gasses have unique____ - used to determine elements in a mixture

### Bohr

WHO proposed that the attractive force between the positive nucleus and negative electrons kept the electrons in orbit

### Bohr

WHO Stated that the electrons were only allowed to be in certain orbits - electrons could jump from one orbit to the next, but could never be in between the circular orbits

### ground state

At ordinary temperatures, electrons remain in the

### absorbed

When a light shines on the atom, only the photon whose energy matches the energy difference between the two levels is

### dark lines

Absorbed photons account for the ___ in the absorption spectrum

### spontaneous emission

Once an electron is in an excited state, there is a certain probability that it was "fall" back down to the ground state by emitting a photon - called

### The emitted photons

cause the bright lines on an emission spectrum

### Dual Nature of Light

Theory is that all EM waves consist of photons that have no mass, but carry energy and have momentum

### particle and a wave

Light is both a

### frequency

Energy and momentum of light increases with an increase in

### Louis deBroglie

1924 - _____ proposed that all matter, not just light, behaved as both waves and particles

### deBroglie

WHO hypothesized that all matter also behaved like waves, this would mean that electrons should interfere and diffract

### diffract

All matter should_____, although larger object's have such small wavelengths that there are no apertures through which they could pass

### one & two

The first orbit contains____ wavelength, the second orbit ___ wavelengths

### electron's wavelength

The circumference of the orbit must equal an integral number of the

### Heisenberg's Uncertainty Principle

One cannot know the position and momentum of a particle at the same time -

### Erwin Schrödinger

WHO proposed that a particle can be represented by a value, ψ, called the wave function

### given position

The quantity ψ2 is proportional to the probability of finding an electron at a

### Nucleons

found in nucleus, protons (positive) and neutrons (no charge)

### Mass number (A) -

number of nucleons

### Atomic number (Z) -

number of protons

### mass number - atomic number

Neutron number (N) - number of neutrons ____-_____

### Isotope

same element (Z), but different mass because different N value

### atomic numbers (Z)

Elements are identified by their

### (u)

Used for atomic mass

### rest energy

A particle has a certain amount of energy due to its mass

"Mega" =

### strong force

holds nucleus together, overcomes the repulsion of the positive charges

### subatomic particle

Strong force exists between all ____, not just protons

### short ranges

strong forces only appears at ____ (10-15m) - for longer distances it is practically nonexistent

### charge

strong forces are Independent of___

### neutrons

help stabilize the nucleus

### neutrons....protons

Heavier nuclei need more ____ than ___- for stability

### unstable nuclei

For elements above Z (atomic number) = 83, adding neutrons is not enough to stabilize the nucleus - these elements have ____

### nuclei elements

Elements with unstable nuclei will decay into two small _____

### mass deficit

A stable nucleus's mass is less than the mass of its parts - called

### binding energy

This difference in mass is attributed to the energy needed to hold the nucleus together - called

### Nuclear decay -

the breaking apart of an unstable nucleus into two stable nuclei

### particles, light

Radiation is emitted with the two nuclei - as____,____ or both

### Parent nucleus

- starting nucleus

### Daughter nucleus

- the new, stable nuclei

### Alpha Decay

The parent nucleus looses two protons and two neutrons

### 2

Alpha decay: Atomic Number (A) decrease by ___ for the daughter nucleus

### 4

Alpha decay: Atomic mass (Z) decreases by ___ for the daughter

### 1

Beta decay: The atomic number (Z) of the daughter is___ less/___ more than that of the mother - the atomic mass (A) does not change

### Beta decay

changes the neutron/proton ratio in the parent nucleus - this affects the parent's nuclear stability

### Neutrinos

_____ are also emitted in beta decay - needed to conserve momentum and energy in beta decay reactions - symbol, ν (nu)

### Antineutrinos

antiparticle of neutrinos, symbol, ṽ

### antineutrinos

Electrons are accompanied by

### neutrinos

Positrons are accompanied by

### Gamma Decay

Emission of high energy photons

### Gamma Decay

No change in mass or atomic number of daughter nucleus

### decay

If the daughter nucleus is stable (mass = periodic table mass) the___ stops

### decay series

Unstable daughters become parents for a new decay, leading to a ____

Decay constant indicates the rate of ____

### activity

is the rate at which a sample decays over a time period

### unit Becquerel (Bq) = 1 decay/second

unit for activity

= -∆N/∆t

### A curie - 1 Ci = 3.7 x 1010Bq

another unit for activity

### half life

Amount of time it takes for half a sample to decay

### Exponential relationship

- amount remaining over a certain time period

### Fission

- Large nucleus splits into two smaller nuclei, this releases energy

### Daughter

____nuclei are more tightly bound and have less mass than parent nucleus

### lighter

The____ nuclei have more binding energy than the parent nucleus

### chain reaction

Fission usually occurs as a

### Critical mass -

minimum amount of nuclides needed to sustain a chain reaction

### fusion

unites two smaller nuclei to make a larger nucleus - generates energy

### Strong force -

binds neutrons and protons, strongest of fundamental forces, short ranged

### Electromagnetic force -

causes attraction/repulsion of charged particles, hold atoms/molecules together, long ranged

### Weak Force -

short-ranged involved in beta decay.

### Gravitational force -

long-ranged, holds planets/stars in place, weakest of the forces

### Leptons

have no measurable size or structure and do not seem to break down into smaller parts

### hardons

Strongly interacting particles - made up of mesons and baryons

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