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Chapter 4 Arrangement of Electrons in Atoms

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Duality of light explained photoelectric effect! ... Electrons have a dual wave-particle nature. Heisenberg Uncertainty Principle ... – PowerPoint PPT presentation

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Title: Chapter 4 Arrangement of Electrons in Atoms


1
Chapter 4Arrangement of Electrons in Atoms
2
Light can act as a ______________.
? wavelength (lambda) ? frequency
waves/sec (nu), measured in Hertz, Hz 1/s
3
c ? ?
  • c speed of light (3.0 x 108 m/s)
  • What is the frequency of a beam of red light
    whose wavelength 659 nm?

4
_________ _____________ is the only
electromagnetic (EM) radiation we can see
  • electromagnetic radiation (EM) form of energy
    that travels through space as a __________

5
Light can also act as a ____________
  • Supported by 2 experiments
  • Photoelectric effect
  • Hydrogen atom spectrum

6
Particle description of light
  • Max Planck, 1900 studied ___________ of light
    by hot objects
  • Proposed that energy is not ____________
    continuously but in small little ___________
    called _____________ This is a particle
    property
  • quantum min amt of energy than can be lost or
    gained by an atom
  • Energy ? _______________

7
Planck proposed the following relationship
between a quantum of energy and its frequency of
radiation
  • Energy ? frequency
  • E ( frequency )
  • where h Plancks constant
  • 6.626 x 10-34 J s (or J/Hz)

8
Duality of light explained photoelectric effect!
Metal must be struck by a photon possessing a
min. amt of E below this amt, the electron
wont leave the metal! More light of the same E
(same ?) just released more electronsnot more
energetic
9
  • Ground state atoms whose electrons are in their
    ___________ energy level
  • Excited state an atom,having __________ E, jumps
    its electron(s) to a higher E level. The electron
    must jump completely from one level to another.

10
  • De-excitation after a short time the electron
    ____________________________ and _____ a photon
    (packet of E) equivalent to the energy difference
    between the 2 steps. The photon will produce a
    spectral line with a discrete wavelength (color)
    associated with it.
  • Continuous spectrumall wavelengths are present
    (i.e.sunlight)
  • Emission (bright line) spectrum limited of
    specific bright lines that are produced by pass
    the light emitted by an excited atom through a
    prism

11
  • Absorption (dark line) spectrum light emitted by
    an excited atom passes through a substance that
    filters out certain wavelengths and thus produces
    a spectrum with missing (dark) lines.
  • Bright lines of an emission spectrum are
    _____________________ as the dark lines of an
    absorption spectrum for a given element.

12
Bohr Model of the Atom, 1913
  • Studied the absorption of light by ___________
  • Absorption of light at definite wavelengths
    corresponds to the definite changes in the E of
    the _______________
  • Electrons can circle the nucleus at ___________
    _____________ distancesonly in allowed paths, or
    orbits (Satellite model)
  • Energy of an electron is ____________ when it is
    in orbits farther away from the nucleus
  • His calculated energy values agreed with the
    observed spectral lines for hydrogen
  • Model did NOT work when applied to multi-electron
    elements ?

13
Duality of light
  • Proposed by Einstein after studying the works of
    Planck and Bohr
  • Light has been traditionally thought of as a
    __________ (it has freq. wavelength)
  • But now.. light can also be thought of as a
    __________ ___ ______ of particles called photons
  • photons particle of EM radiation having _______
    mass and carrying a ______________ of energy
  • Explained photoelectric effect EM radiation is
    absorbed only in whole numbers of photons

14
4-2The Quantum Model of the Atom
15
De Broglie, 1924
  • If light could behave as both a wave and a
    particle, then could an electron (a particle)
    also behave as both a particle and a wave
    ?????????????
  • He said _________ because.
  • Since electrons could only exist at specific
    energies, and E can be equated to frequency (E
    h?), they have wave properties
  • And electrons can be focused like light
    (electron microscopes)
  • particle nature of electrons had already been
    confirmed (cathode rays, oil drop exper, etc.)

16
  • Electrons have a dual wave-particle nature

17
Heisenberg Uncertainty Principle
  • It is impossible to determine simultaneously both
    the __________ and __________ of an electron or
    any other particle

18
Schrodinger Wave Equation, 1926
  • If electrons have wave properties, then wave
    equations can be applied to electrons (and other
    small particles)
  • Laid foundation for __________ ___________
    describes ______________________ the wave
    properties of electrons and other very small
    particles
  • Gives the ______________________ of finding an
    electron at a given place in time around the
    nucleus

19
Quantum Theory (cont)
  • Electrons do NOT travel around the nucleus like
    planets around the sun
  • Electrons exist in certain regions called
    ______________ a 3-D region around the nucleus
    that indicates the _________ location of an
    electron

20
Quantum Numbers
  • Specify the properties of atomic orbitals and the
    properties of electrons in orbitals
  • There are __________ quantum numbers.the first
    three of which come from solutions to
    Schrodingers wave equation

21
Principal Quantum Number, n
  • Indicates the _________ __________ _________
    (or shell) occupied by the electron
  • n 1, 2, 3 etc.
  • The ?n value, the ___________ the electron is
    from nucleus? principal quant also gives
    ________ ________________
  • Total electrons on a level __________
  • Total orbitals on a level n2 since an orbital
    can hold two electrons (2n2/2 n2)

22
Angular Momentum Quantum Number, l
  • Also known as second quantum number
  • Also known as azimuthal quantum number
  • Most energy levels (all but n1) have orbitals of
    different __________, called ____________
  • Describes the ______________ of the orbital
  • orbital shapes possible is equal to the
  • ______ _____________
  • If n3, then there can be 3 orbital shapes
  • The values of l 0, 1, 2,. (n-1)
  • If n3, then l can be ___, ___, or ___.

23
Angular Momentum Quantum Number, l (cont)
  • An orbital LETTER is used to designate each
    shape

24
(No Transcript)
25
Magnetic Quantum Number, ml
  • also known as the 3rd quantum number
  • indicates the orientation of an orbital around
    the nucleus
  • (2 l 1)

26
Magnetic Quantum Number, m (cont)
  • Sum of all orbitals in a sublevel (or E level) is
    a spherical cloud!

27
Spin quantum number, s
  • Describes the spin of the electron
  • Could be either clockwise ( ½) or
    counterclockwise (- ½ )
  • Each orbital can hold a maximum of two electrons,
    a pair, spinning in opposite directions

28
4-3
  • ELECTRON CONFIGURATIONS

29
Hunds Rule
  • Orbitals of equal energy are ________ occupied by
    one electron before any orbital is occupied by a
    second electron, and
  • All electrons in singly occupied orbitals must
    have the same _____

30
Aufbau Principle
  • An electron occupies the ________________ orbital
    that can receive it

31
Noble Gas Notation
  • What is the noble gas electron notation for
    calcium?
  • 1s22s22p63s23p64s2
  • What is the noble gas config for S?
  • 1s22s22p63s23p4

32
PREDICTED
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