Arrangement of Electrons in Atoms

1
Arrangement of Electrons in Atoms
2
Development of a New Atomic Model
3
Light as a wave.
4
Electromagnetic Radiation

• A form of energy
• Exhibits wavelike characteristics
• No medium is required

5
Electromagnetic Radiation

• All Electromagnetic Radiation travels at the same
  rate
• 3.00 x 108 m/s

6
Electromagnetic Radiation
7
Electromagnetic Radiation

• Wavelength
• Frequency
• Amplitude
• Crest
• Trough

8
Wavelength and Frequency

• c ??
• c speed of light
• ? wavelength
• ? frequency

9
Light as a particle.
10
Problems with classical physics.

• Blackbody radiation.
• The photoelectric effect.
• Stability of the atom.

11
Blackbody radiation.

• Heating a piece of metal changes the color from
  red, to orange, to white.
• Classical physics should see all colors
  (energies)
• Could not explain why only certain colors showed
  up.

12
Photoelectric Effect

• Yellow light shone on certain metals
• Nothing happens
• Really bright yellow light (more energy)
• Nothing happens

13
Photoelectric Effect

• Blue light shone on certain metals
• Electrons given off
• Really bright blue light
• More electrons given off but same speed

14
Stability of the atom.

• Why isnt the electron attracted to the nucleus?
• If the electron is circling the nucleus then why
  doesnt it emit radiation and fall into the
  nucleus?

15
Classical Physics revised.
16
Blackbody Radiation

• Max Planck energy delivered in packets,
  quantum.
• If energy is delivered in packets, then
  blackbodies gain energy in packets.
• Only packets of certain frequencies are delivered.

17
Energy and Frequency

• Energy and frequency are related.

18
Energy and Frequency

• E h?
• E Energy, Joules (J)
• h Planck constant, 6.626x10-34 Js
• ? Frequency, Hertz (Hz)

19
The Photoelectric Effect
20
Einsteins Theory

• Einstein theorized the dual nature of light.
• Used the two-slit experiment to verify the
  particle and wave nature of light.

21
Photoelectric Effect

• Einstein proposed that light should be both a
  particle and a wave.
• Coined the term photon (a quantum of light).
• Only certain photons have enough energy

22
Why talk about waves?

• De Broglie determined that all matter behaves as
  waves.
• Electrons are matter.
• Therefore, electrons behave as waves and as
  particles both.

23
Stability of the Atom

• Explained by Niels Bohr using experiments by
  others.
• Looked at the emission line spectrum published by
  Lyman, Balmer, and Paschen

24
Line spectrum.

• Hydrogen only gave a line spectrum when passed
  through a prism.
• Thought that any amount of energy should excite
  the Hydrogen and therefore a continuous spectrum
  should be given.

25
Lyman, Balmer, Paschen

• Investigated Hydrogen gas excited in a tube.
• Passed light through a prism.
• The H2 light emitted a line emission spectrum.
• The line emission spectrum is the Lyman, Balmer,
  Paschen Series.

26
Bohr Model of the Atom

• Bohr proposed that electrons exist on quantized
  orbits
• The orbits have a defined amount of energy

27
Bohr Model of the Atom

• Ground State lowest energy state
• Excited State gained energy
• Must gain energy to get to an excited state

28
Bohr Model of the Atom

• Explains Lyman, Balmer, Paschen
• Electron gains energy and jumps orbits
• Electron is unstable
• Electron drops back to ground state, giving off
  energy (light)

29
Bohr Model of the Atom

• Since the orbits have only certain energies, only
  certain wavelengths exist.
• Also mathematically verified theory.

30
Bohr Model of the Atom.

• Proposed Orbits
• When the electron is in an orbit, it has a
  defined amount of energy.
• The electron can not exist between orbits.

31
Bohr Model of the Atom

• The electron must absorb energy to move orbits.
• The electron emits the same amount of energy as
  it absorbs.
• The energy difference is the difference between
  energy levels.

32
Bohr Model of the Atom

• 1st orbit is a certain distance from the nucleus.
• The higher the orbit, the more energy.

33
Bohr Model of the Atom

• Orbits are not equally spaced
• Since the orbit has inherent energy, the electron
  has energy from the beginning.
• Only explains single electron atoms

34
The Quantum Model of the Atom
35
Electron as a wave De Broglie

• All matter behaves as waves.
• Electron exhibits wavelike properties.

36
Electron as a wave De Broglie

• The electron is a wave confined to the nucleus.
• The electron can be bent (diffraction) like a
  wave.
• The electron can cancel itself out (interference)
  like a wave

37
Electron as a waveHeisenberg

• Heisenberg Uncertainty Principle
• It is impossible to know the position and
  velocity of an electron at the same time.
• Once you measure it, you change it.

38
Electron as a wave Schrodinger

• Developed Schrodinger wave equation.
• Only waves of specific energy solves the equation

39
Electron as a wave Schrodinger

• Paved the way for Quantum Theory
• Quantum Theory describes mathematically the
  movement of very small things.
• Solving Schrodinger wave equation gives quantum
  numbers.

40
Quantum Model and Electron Configuration.
41
Quantum Model

• Has Orbitals
• An orbital is a fuzzy region of probable electron
  placement (90)
• Orbitals have distinct shapes dependent upon
  amount of energy of the electron.

42
Quantum Model

• Orbital shapes are given symbols
• s, p, d, f, etc.

43
Quantum Model has rules for electron placement.
44
Aufbau Principle

• Lazy mans rule.
• Aufbau Principle - electron will occupy the
  lowest energy orbital available.

45
Hunds Rule

• Summer camp rule.
• Orbitals of equal energy are each occupied by one
  electron before any orbital is occupied by a 2nd
  electron.

46
Pauli Exclusion Principle

• No two electrons in an atom can have the same 4
  quantum numbers
• Quantum numbers describe the placement of
  electrons in an orbital
• Only allows for 2 electrons per orbital shape

47
Electron configuration.

• Use the aforementioned rules to determine
  electron configuration notation.

48
Orbital Notation

• Uses arrows and lines to show electrons and
  orbitals

49
Energy Levels

• Highest occupied energy level is the highest
  energy level with an electron.
• Ex. 1s22s22p63s23p64s23d7
• Inner shell electrons are all of the electrons
  not on the outside.
• Ex. 1s22s22p63s23p64s23d7

50
Noble Gas Configuration

• A Noble gas configuration has the outermost s and
  p orbitals filled.
• Example 1s22s22p6, 1s22s22p63s23p6
• Noble Gas Shortcut - use the Noble gas before the
  element (except He).
• Example Br Ar4s23d104p5