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Try to find visual of uncertainty principle.

Try to find visual of uncertainty principle. Electronic Structure of Atoms. Chapter 6. Niels Bohr tried to explain the location of electrons…. Based his ideas on the relationship between matter and light (electromagnetic radiation)

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Try to find visual of uncertainty principle.

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  1. Try to find visual of uncertainty principle.

  2. Electronic Structure of Atoms Chapter 6

  3. Niels Bohr tried to explain the location of electrons…. Based his ideas on the relationship between matter and light (electromagnetic radiation) We need background information on electromagnetic radiation before we can discuss Bohr’s ideas

  4. LIGHT Properties of light: • Part of the electromagnetic radiation spectrum • Has a constant velocity (symbol is c) c = 3.00 X 108 m/sec *watch the units! There are 2 theories that can explain light: wave theory & particle theory. on AP equation sheet!

  5. WAVE THEORY OF LIGHT BEHAVIOR light has a wave-like nature wavelength ( l ) - distance per cycle of wave frequency ( n ) - number of cycles per unit of time

  6. Velocity is related to wavelength and frequency on AP equation sheet! For any wave, velocity = l • n For any electromagnetic wave, c = l • n 3.00x108 m/sec= l • n • l and n are inversely related for electromagnetic waves

  7. Electromagnetic Radiation Spectrum - thetype of radiation is related to its wavelength -11 -9 -7 -5 -3 -1 1 3 10 10 10 10 10 10 10 10 (l in cm) | | | | | | | | | | | | | | | | | | | | | Gamma | X-rays | Ultra |V| Infrared | Micro | TV & radio radiation | | Violet |i| light | waves | signals | | light |s| | | smaller wavelength larger wavelength larger frequency smaller frequency larger energy smaller energy VISIBLE LIGHT

  8. PARTICLE THEORY OF LIGHT BEHAVIOR • Max Plank figured out that light can be released from and absorbed by atoms in “chunks” that have a minimum size. • Light is made up of particles called photons or quanta- bundles of energy

  9. There is a mathematical equation that ties these 2 theories together Energy of photon = (Plank’s constant) (frequency) E = h • n h = Plank’s constant = 6.63 X 10-34 Joule-second (J-s) E and n are directly related E and l are inversely related on AP equation sheet!

  10. Niels Bohr Model of the Atom Electrons are found in “orbits” that surround the nucleus. The concept of an orbit means that the electron travels around the nucleus at a fixed distance and at a fixed speed that keeps it on that particular orbit. Yes, Bohr was wrong about orbits….let’s pretend he meant energy levels (because that’s what they really are!)

  11. Bohr Model (cont.) When an electron absorbs a certain amount of energy, called a “quanta,” it can jump to an energy level farther from the nucleus.

  12. Bohr Model When electrons absorb energy to jump up a level, they immediately release the same amount of energy to get back to the ground state.

  13. Bohr Model • Sometimes, the energy that is absorbed or released by excited electrons can be seen as different colors of light! • The color depends on the wavelength or energy of the light emitted!

  14. Neils Bohr • Examined the light released by atoms of certain elements • Worked mostly with hydrogen since it has only 1 electron • Bohr used a spectroscope to analyze the light released from a vacuum tube - the result is a bright line spectrum more commonly called an EMISSION SPECTRUM (black background with bright colored lines)

  15. EMISSION SPECTRUM Only certain wavelengths or photon energies of light are present in the emission spectrum An element’s emission spectrum is unique to that element (like a fingerprint!)

  16. Energy level diagram • U V • I R • Visible • 7 • 6 • 5 • H emission spectrum • 4 • A • D • B • C • 3 • violet red • E • N • E • R • G • Y • 4 x 10-5λ 7 x 10-5 • smaller λ larger λ • 2 • A B C D • larger E smaller E Arrow D is the longest arrow in the visible region which means it has the highest energy and corresponds to the violet line in hydrogen’s emission spectrum. Arrow A is the shortest arrow in the visible region which means it has the lowest energy and corresponds to the red line in hydrogen’s emission spectrum. • again, 21 possible emission lines • again, also 21 possible absorption lines • absorption lines (arrows) would point UP • 1

  17. Calculations: • To find the energy associated with each orbit in the hydrogen atom, Bohr used the equation: • Subtract the energy of the orbits between which an electron moves to find the energy released/absorbed. • Use E=hν to convert energy to frequency • Use c=λν to convert frequency to wavelength • These correspond to the colors seen in the emission spectrum! On AP Equation Sheet!

  18. Bohr tried to apply his ideas about electron behavior of hydrogen atoms to atoms of other elements. Bohr tried to explain the arrangement of elements on the periodic table by showing that elements in acolumn of the periodic table have similar chemical properties because they have similar electron structures.

  19. does not work for #21 scandium Ca K

  20. After Bohr…. • Loius De Broglie…if light can behave like matter (photons)…can matter behave like a wave?? YEP! Λ = wavelength (m) h= Plank’s constant (J-sec) m= mass (kg) V = velocity (m/sec) on AP equation sheet!

  21. The Uncertainty Principle • Werner Heisenberg….because of the dual nature of matter both the path and velocity of a particle with the size and mass of the electron can not be determined at the same instant in time - in other words, electrons cannot be in orbits! • *The uncertainty in the calculation of the position of the electron is larger than the entire atom because the electron is so small!

  22. Breakdown of the Bohr model of the atom • Does not explain the behavior of atoms with more than 20 electrons 2. Violates the Heisenberg Uncertainty Principle

  23. SCHRÖDINGER • He developed the idea of wave mechanics - treating the electron as if it had wave-like properties. • He mathematically considered the region of space in the atom where an electron of a given energy would MOST PROBABLY BE LOCATED. • This is a radical departure from earlier work. Schrödinger says to forget exactly where the electron is (Heisenberg says we can’t find out anyway) and concentrate on where the electron MIGHT be.

  24. RESULTS OF THE MODERN THEORY OF ELECTRON BEHAVIOR • The math involved in wave equations is very complicated and beyond the scope of this course. Fortunately, the results of this theory are easier to understand than the mathematics.

  25. ORBITAL - The region of space in an atom where it is highly probable that an electron of a given energy will be located - About 90 % of the solution set to the wave equation - Max of 2 electrons/orbital

  26. Energy Level Diagram Each box = electron Each column = orbital Each group = sublevel Big # out front = Energy level

  27. Multi-electron atoms: • Atoms fill the lowest energy positions first • 2 methods to know the order: • Periodic table • Wavy line diagram

  28. s p The Periodic Table n 1 d (n-1) 2 3 1 4 5 6 7 f (n-2)

  29. Wavy-line Diagram

  30. Principle Quantum Number (n) • Indicates a specific energy LEVEL (energy levels values found by Bohr) • Indicates the relative size of the energy level - larger value means larger size • Indicate the relative energy of the electron – larger value means higher energy. • Possible values are n = 1, 2, 3, 4, 5, 6, 7, ...

  31. Angular Momentum Quantum Number () • Indicates a specific energy SUBLEVEL • The number of energy sublevels per energy level is equal to the value of the energy level (example: 3 sublevels in the 3rd energy level) • Possible values are  = 0, 1, 2, 3, ..., max. value of n-1 • more commonly = s, p, d, f, ... (alphabetically after f)

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