BIG topics... Light (electromagnetic radiation) particle/wave dual nature of light c, λ, ט, E &...
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Transcript of BIG topics... Light (electromagnetic radiation) particle/wave dual nature of light c, λ, ט, E &...
BIG topics... Light (electromagnetic radiation)
particle/wave dual nature of light c, λ, ט , E & h
Quantum theory (wave mechanical model) Bohr model of Hydrogen atom absorption/emission quantum numbers & orbital shapes
Electron configurations orbital, e- configuration noble gas notation Aufbau, Pauli & Hund
WavesWaves Wavelength () - length of one
complete wave. Common units: m or nm
Frequency () - # of waves that pass a point during a certain time periodCommon Units: hertz (Hz) = 1/s = s-1
Amplitude (A) - distance from the origin to the trough or crest
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Wavelength and FrequencyWavelength and Frequency
E = h
c = c = speed of light (3.0 x 108 m/s) = frequency (s-1)= wavelength (m)
E = energy (Joules or J)h= Planck’s constant (6.626 x10-34 J s) = frequency (s-1)
“nu” “lamda”
Highest energy
Moderate energy
Lowest energy
Visible part of EM SPectrumVisible part of EM SPectrum
PRISM
Slit
Ray of
White Light
Waves 1/33,000” long
Waves 1/70,000” long
RedOrangeYellowGreenBlueIndigoViolet
400 nm – 700 nm
Electromagnetic SpectrumElectromagnetic Spectrum
GIVEN:
h x 10-34 J s
c = 3.00 x 108 m/s
= ?
= 1.0 x 10-3 nm = ???? m
WORK: = c = 3.00 108 m/s 1.0 x 10-12 m = 3.0 x 1020 s-1
Find the energy of a photon with a Find the energy of a photon with a wavelength of 1.00 x 10wavelength of 1.00 x 10-3-3 nm. nm.
E = hvc = λv
= (6.626 x 10-34 J s)(3.0 x 1020s-1)
E = 1.99 x 10-13 J
E = hc λ
Quantum TheoryQuantum Theory
Max Planck Max Planck (1900)(1900)
ObservedObserved - emission of light from hot - emission of light from hot objectsobjects
ConcludedConcluded - energy is - energy is emitted in small, specific emitted in small, specific amounts (quanta)amounts (quanta)
QuantumQuantum - minimum amount of energy - minimum amount of energy gained or lost by an atomgained or lost by an atom
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Continuous vs. Quantized Continuous vs. Quantized EnergyEnergy
Ene
rgy
A Bcontinuous quantized
Acontinuous
Bquantized
Bohr Model of Bohr Model of HydrogenHydrogen
Nucleus
Possible electron orbits
eGreat theory, BUT it turned out to be totally wrong!! Next week we’ll see a better theory
Further away from nucleus means higher energy level…
Excitation of Hydrogen Atoms
Return to Ground State
Emission Spectrum of Hydrogen
1 nm = 1 x 10-9 m = “a billionth of a meter”
410 nm 434 nm 486 nm 656 nm
Continuous and Line Spectra
light
Na
H
Ca
Hg
400 450 500 550 600 650 700 750 nm
Visiblespectrum
(nm)
An Excited Lithium Atom
Photon ofred lightemitted
Li atom inlower energy state
Excited Li atom
Ene
rgy
Preview....Orbital ShapesPreview....Orbital Shapes