Electromagnetic Spectrum radiation with both electric and magnetic components

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Electromagnetic Spectrumradiation with both
electric and magnetic components
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Electromagnetic Radiation

• Electromagnetic wave
• wavelength
• frequency
• amplitude

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Wavelength Frequency Amplitude
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Plancks Quantum Theory

• E hn hc/l
• where nl c
• E ? energy
• h ? Planck's constant
• n ? frequency
• c ? speed of light
• l ? wavelength

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Photoelectric Effect

• the emission of electrons by substances, such as
  metals, when light falls on their surfaces.

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Photoelectric Effect
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a quantum, unit, of electromagnetic energyLine
Spectrum
Photons

• spectrum emitted by a luminous gas or vapor
• appears as distinct lines characteristic of the
  various elements present

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Emission Spectrum

• spectrum of bright lines, bands, or continuous
  radiation
• characteristic of a specific emitting substance

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Line Emission Spectrum
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Energy Transitions

• Ground State - lowest energy state for electrons
  in an atom
• Excited State - any energy state above the ground
  state

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Absorption Spectrum

• light shinning on a sample causes electrons to be
  excited from the ground state to an excited state
• wavelengths of that energy are removed from
  transmitted spectra

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Bohr Model for the Hydrogen Atom

• E -B/n2
• E (-2.179 ? 10-18 J/part.)
• (6.022 ? 1023 part./mole)
• (1 kJ/103 J)/n2
• (-1312 kJ/mol)(1/n2)
• where n ? quantum number
• 1, 2, 3, 4, 5, 6, 7, etc

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Bohr Model

• for hydrogen
• ground state n 1
• excited state n gt 1

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Hydrogen Spectrum

• E (-2.179 ? 10-18 J)(1/ni2 - 1/nf2)
• where ni initial state quantum number
• nf final state quantum number

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Hydrogen Spectrum
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Line Spectra

• Lyman series ? ultraviolet
• n gt 1 ? n 1
• Balmer series ? visible light
• n gt 2 ? n 2
• Paschen series ? infrared
• n gt 3 ? n 3

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Quantum Mechanics

• Heissenberg Uncertainty Principle - it is
  impossible to know precisely both the location
  and momentum of an electron

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Orbitals

• region of probability of finding an electron
  around the nucleus
• 4 types ? s p d f
• maximum of 2 electrons per orbital

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Pure Atomic Orbitals

• shape of orbitals / energy level
• s spherical 1
• p dumbbell 3
• d complex 5
• f very complex 7

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Atomic Orbitals
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Quantum Numbers
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Quantum Numbers

• n ? energy level
• (1, 2, 3, 4, 5, 6, 7, etc.)
• l ? type of orbital
• (s l0 p l1 d l2 f l3)
• ml ? which orbital
• (one value per orbital -l ? -l1 ? 0 ? l-1 ? l)
• s ? direction of spin
• (-1/2 or 1/2)

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Electrons
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Electronic Configurationand the Periodic Table
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Electronic Configurations

• The shorthand representation of the occupancy of
  the energy levels (shells and subshells) of an
  atom by electrons.

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Electronic Configuration

• H atom 1 electron 1s1
• He atom 2 electrons 1s2
• Li atom 3 electrons 1s2, 2s1
• Cl atom 17 electrons
• 1s2, 2s2, 2p6, 3s2, 3p5

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Electronic Configuration

• As atom
• 33 electons
• 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p3
• or
• Ar 4s2, 3d10, 4p3

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Electronic Configuration

• negative ions
• add electron(s), 1 electron for each negative
  charge
• S-2 ion
• (16 2)electrons
• 1s2, 2s2, 2p6, 3s2, 3p6

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Electronic Configuration

• positive ions
• remove electron(s), 1 electron for each positive
  charge
• Mg2 ion
• (12-2)electrons
• 1s2, 2s2, 2p6

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Lewis Electron Dot Structures
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Trends in thePeriodic Table

• atomic radius
• ionic radius
• ionization energy
• electron affinity

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Atomic Radius

• decrease left to right across a period
• as nuclear charge increases, number of electrons
  increase however, the nucleus acts as a unit
  charge while the electrons act independently,
  pulling electrons towards the nucleus, decreasing
  size

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Atomic Radius

• increase top to bottom down a group
• each additional electron shell shields the
  outer electrons from the nuclear charge
• Zeff Z - S
• where Zeff ? effective nuclear charge
• Z ? nuclear charge, atomic number
• S ? shielding constant

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Atomic Radius

• increases from upper right corner to the lower
  left corner

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Atomic Radius ofMain Group Elements
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Atomic Radius ofs-, p-, and d- Block Elements
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Nuclear Magnetic Resonance
http//mrsec.wisc.edu/edetc/NMR/index.html
The most common nuclei studied using NMR are
H-1, C-13, F-19 and P-31. Most MRI studies
involve the H-1 nuclei in water. When these
nuclei are exposed to an external magnetic
field, their spins can be parallel or
anti-parallel to this external field.
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Ionic Radius

• same trends as for atomic radius
• positive ions smaller than atom
• negative ions larger than atom

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Ionic Radius

• Isoelectronic Series
• series of negative ions, noble gas atom, and
  positive ions with the same electronic
  configuration
• size decreases as positive charge of the
  nucleus increases

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Isoelectronic Series
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Sizes of Ions and their Neutral Atoms
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Ionization Energy

• energy necessary to remove an electron to form a
  positive ion
• low value for metals, electrons easily removed
• high value for non-metals, electrons difficult to
  remove
• increases from lower left corner of periodic
  table to the upper right corner

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Ionization Energies

• first ionization energy
• energy to remove first electron from an atom
• second ionization energy
• energy to remove second electron from a 1 ion
• etc.

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First Ionization Energies
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Electron Affinity

• energy released when an electron is added to an
  atom
• same trends as ionization energy, increases from
  lower left corner to the upper right corner
• metals have low EA
• nonmetals have high EA

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Electron Affinities