modern atomic theory (a.k.a. the electron chapter!) chemistry 1: chapters 5, 6, and 7 chemistry 1...

Modern Atomic Theory(a.k.a. the electron chapter!)

Chemistry 1: Chapters Chemistry 1: Chapters 5, 6, and 75, 6, and 7

Chemistry 1 Honors: Chemistry 1 Honors: Chapter 11Chapter 11

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ELECTROMAGNETIC ELECTROMAGNETIC RADIATIONRADIATION

ELECTROMAGNETIC ELECTROMAGNETIC RADIATIONRADIATION

Electromagnetic radiation.

Electromagnetic Electromagnetic RadiationRadiation


• Most subatomic particles behave as Most subatomic particles behave as PARTICLES and obey the physics of PARTICLES and obey the physics of waves.waves.

wavelength Visible light

wavelength

Ultaviolet radiation

Amplitude

Node



• Waves have a frequencyWaves have a frequency• Use the Greek letter “nu”, Use the Greek letter “nu”, , for , for

frequency, and units are “cycles per frequency, and units are “cycles per sec”sec”

• All radiation: All radiation: • • = c = cwhere c = velocity of light = 3.00 x 10where c = velocity of light = 3.00 x 1088 m/secm/sec



Electromagnetic Electromagnetic SpectrumSpectrum

Electromagnetic Electromagnetic SpectrumSpectrum

Long wavelength --> small frequencyLong wavelength --> small frequency

Short wavelength --> high frequencyShort wavelength --> high frequency

increasing increasing frequencyfrequency

increasing increasing wavelengthwavelength

ElectroElectromagneticmagnetic SpectrumSpectrum

ElectroElectromagneticmagnetic SpectrumSpectrum

In increasing energy, RIn increasing energy, ROOYY GG BBIIVV

Excited Gases Excited Gases & Atomic & Atomic StructureStructure

Atomic Line Emission Atomic Line Emission Spectra and Niels Spectra and Niels

BohrBohr

Atomic Line Emission Atomic Line Emission Spectra and Niels Spectra and Niels

BohrBohrBohr’s greatest contribution to Bohr’s greatest contribution to

science was in building a simple science was in building a simple model of the atom. It was based model of the atom. It was based on an understanding of theon an understanding of the LINE LINE EMISSION SPECTRAEMISSION SPECTRA of of excited atoms.excited atoms.

• Problem is that the model only Problem is that the model only works for Hworks for HNiels BohrNiels Bohr

(1885-1962)(1885-1962)

Spectrum of White Spectrum of White LightLight

Line Emission Line Emission Spectra Spectra

of Excited Atomsof Excited Atoms

Line Emission Line Emission Spectra Spectra

of Excited Atomsof Excited Atoms• Excited atoms emit light of only certain wavelengths

• The wavelengths of emitted light depend on the element.

Spectrum of Spectrum of Excited Hydrogen GasExcited Hydrogen Gas

Line Spectra of Other Line Spectra of Other ElementsElements

The Electric PickleThe Electric Pickle• Excited atoms can

emit light.• Here the solution in a

pickle is excited electrically. The Na+ ions in the pickle juice give off light characteristic of that element.

Light Spectrum Lab! Slit that Slit that allows light allows light insideinside

Line up the slit so Line up the slit so that it is parallel with that it is parallel with the spectrum tube the spectrum tube (light bulb)(light bulb)

ScaleScale

Light Spectrum Lab!

• Run electricity through various gases, creating light

• Look at the light using a spectroscope to separate the light into its component colors

• Using colored pencils, draw the line spectra (all of the lines) and determine the wavelength of the three brightest lines

• Once you line up the slit with the light, then look to the scale on the right. You should see the colored lines under the scale.

Slit that Slit that allows light allows light insideinside

EyepieceEyepiece

ScaleScale

Light Spectrum Lab!

Atomic SpectraAtomic SpectraAtomic SpectraAtomic Spectra

+Electronorbit

One view of atomic structure in early 20th One view of atomic structure in early 20th century was that an electron (e-) traveled century was that an electron (e-) traveled about the nucleus in an orbit.about the nucleus in an orbit.

Atomic Spectra and BohrAtomic Spectra and BohrAtomic Spectra and BohrAtomic Spectra and BohrBohr said classical view is wrong. Bohr said classical view is wrong. We need a new theory — now called We need a new theory — now called

QUANTUMQUANTUM or or WAVE MECHANICSWAVE MECHANICS..

e- can only exist in certain discrete orbitse- can only exist in certain discrete orbits

e- is restricted to e- is restricted to QUANTIZEDQUANTIZED energy energy state (quanta = bundles of energy)state (quanta = bundles of energy)

Schrodinger applied idea of e- behaving Schrodinger applied idea of e- behaving as a wave to the problem of electrons as a wave to the problem of electrons in atoms.in atoms.

He developed the He developed the WAVE EQUATIONWAVE EQUATION

Solution gives set of math Solution gives set of math expressions called expressions called WAVE WAVE FUNCTIONS, FUNCTIONS,

Each describes an allowed energy Each describes an allowed energy state of an e-state of an e-

E. SchrodingerE. Schrodinger1887-19611887-1961

Quantum or Wave Quantum or Wave MechanicsMechanics

Quantum or Wave Quantum or Wave MechanicsMechanics

Heisenberg Heisenberg Uncertainty Uncertainty

PrinciplePrincipleProblem of defining nature of Problem of defining nature of

electrons in atoms solved by electrons in atoms solved by W. Heisenberg.W. Heisenberg.

Cannot simultaneously define Cannot simultaneously define the position and momentum the position and momentum (p= m•v) of an electron.(p= m•v) of an electron.

We define e- energy exactly We define e- energy exactly but accept limitation that we but accept limitation that we do not know exact position.do not know exact position.

Problem of defining nature of Problem of defining nature of electrons in atoms solved by electrons in atoms solved by W. Heisenberg.W. Heisenberg.

Cannot simultaneously define Cannot simultaneously define the position and momentum the position and momentum (p= m•v) of an electron.(p= m•v) of an electron.

We define e- energy exactly We define e- energy exactly but accept limitation that we but accept limitation that we do not know exact position.do not know exact position.

W. HeisenbergW. Heisenberg1901-19761901-1976

modern atomic theory (a.k.a. the electron chapter!) chemistry 1: chapters 5, 6, and 7 chemistry 1...

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