Chapter 6 Modern Atomic Theory. Review… Dalton Thomson Rutherford –Model doesn’t explain how...
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Transcript of Chapter 6 Modern Atomic Theory. Review… Dalton Thomson Rutherford –Model doesn’t explain how...
Review…
• Dalton• Thomson• Rutherford
– Model doesn’t explain how the negative electron can stay in orbit and not be attracted to the positive proton
Electromagnetic Radiation
• All waves can be described in 3 ways:– Amplitude –
– Wavelength ( ):l
– Frequency ( ):n
Electromagnetic Radiation
• Speed of light in air: Electromagnetic radiation moves through a vacuum at speed of
• Since light moves at constant speed there is a relationship between wavelength and frequency:
Wavelength and frequency are
inversely proportional
Photoelectric Effect
• The emission of
– Albert Einstein (1905) used Planck’s equation to explain this phenomenon;• proposed that light consists of
• Photon =
Photoelectric Effect
• He (Einstein) explained that the photoelectric effect would not occur if the frequency and therefore
• Analogy:– 70 cents placed in soda machine: no
soda– 30 cents more and you will get your
soda
Niels Henrik David Bohr
• 1885-1962• Physicist• Worked with
Rutherford– 1912
• Studying line spectra– of hydrogen
The Bohr Atom• Nucleus with • Electrons move in
• When an electron moves from one state to another the energy lost or gained is in
• Each line in a spectrum is produced when an electron moves from
The Bohr Atom
• Model didn’t seem to work with atoms with more than one electron
• Did not explain chemical behavior of the atoms
LineSpectrum• Elements
in gaseous states give
off colored light
– High temperature or high voltage– Always the same– Each element is unique
• Spectra
Line Spectrum• Each band of color is produced by
light of a different • Each particular wavelength has a
definite
• Each line must therefore be produced by emission of photons with
Wave Matters…
•Louis de Broglie (1924)
•Proposed that electrons might have a
•Used observations of normal wave activity
Problems…
• Wave theory does not explain– Heated iron gives off heat
• 1st red glow yellow glow white glow
– How elements such as barium and strontium give rise to green and red colors when heated
Beginnings…
• Max Planck (1858-1947)– Proposed that there is a fundamental
restriction on the amounts of energy that an object emits or absorbs, and he called each of these pieces of energy
• Energy is released in
Beginnings
• A quantum is a finite quantity of energy that can be gained or lost by an atom
• This constant, h, is the same for all electromagnetic radiation
Bohr’s Equation
•En = (-RH)(1/n2)
• Where RH = 2.18 x 10-18J• And n = principal quantum
number, 1 to infinity
Jumping electrons…
• If an electron moves from one energy level to another, the change in energy can be determined by the following equation:
• E = Ef – Ei = hν• Or simply: E = hv
– Where h=6.626 x 10-34 J s
Finally… Matter waves
• All moving particles
• Some is apparent, some not.• De Broglie’s equation
λ =h
mν
Smart guy…
•Erwin Schrodinger (1926)
•Used mathematical understanding of wave behavior – devised an equation that treated electrons moving around nuclei as waves
•Quantum Theory
Quantum Theory
• Describes mathematically the wave properties of electrons and other very small particles
• Applies to all elements (not just H)
Energy Levels of Electrons
• Principle energy levels– Designated by letter n– Corresponds to the– Each level divided into sublevels
• 1st energy level has• 2nd energy level has• Etc.
Quantum Numbers• Orbital Quantum Number:
– Indicates the shape of an orbital– (subshell or sublevels)– s, p, d, f Principal Quantum # Orbital Quantum
#1 2 3 4
Orbitron
• For a full view of the different orbital shapes, visit
• http://www.shef.ac.uk/chemistry/orbitron/index.html
Rules for Orbital Filling• Pauli’s Exclusion Rule
– No two electrons have
• Hund’s Rule– Electrons will remain
1s 2s 2p 3s 3p
Rules for Orbital Filling
• Diagonal Rule– The order of filling
once the d & f sublevels are being filled
– Due to energy levels
Application of Quantum Numbers
• Several ways of writing the address or location of an electron
• Lowest energy levels are filled first• Electron Configuration:
12C: 32S: