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  • electromagnetic radiation

    All objects emit


    What type of radiation a body will emit depends on its

    higher energy EM wave emitted

    Higher temperature =


    An ideal system that absorbs all incoming radiation is called a

    Blackbody radiation -

    emitted by blackbody, emits radiation only based on its temperature

    Max Planck

    Developed a formula that explained blackbody radiation


    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

    Planck's Equation:

    E = nhf


    is the quantum number (energy level, usually 1)


    is planck's constant: 6.63x10-34 Js


    is the frequency of the light wave

    electronvolt (eV) - 1eV

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


    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


    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


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


    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


    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


    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


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


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


    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


    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


    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


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


    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 ____-_____


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

    atomic numbers (Z)

    Elements are identified by their


    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


    strong forces are Independent of___


    help stabilize the nucleus


    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, beta, and gamma

    Three types of radiation -

    Alpha Decay

    The parent nucleus looses two protons and two neutrons


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


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


    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


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


    antiparticle of neutrinos, symbol, ṽ


    Electrons are accompanied by


    Positrons are accompanied by

    Gamma Decay

    Emission of high energy photons

    Gamma Decay

    No change in mass or atomic number of daughter nucleus


    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 ____

    radioactive decay

    Decay constant indicates the rate of ____


    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


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


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


    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


    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


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


    Strongly interacting particles - made up of mesons and baryons

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