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Arrangement of Electrons in Atoms

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Arrangement of Electrons in Atoms Development of a New Atomic Model Wave Description Of Light Electromagnetic Radiation: form of energy that exhibits wavelike ... – PowerPoint PPT presentation

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Date added: 14 July 2020
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Title: Arrangement of Electrons in Atoms


1
Arrangement of Electrons in Atoms
  • Development of a New Atomic Model

2
Wave Description Of Light
  • Electromagnetic Radiation
  • form of energy that exhibits wavelike behavior as
    it travels through space.
  • EX visible light, X-ray, Ultraviolet and
    inferred light, microwaves, and radio waves.
  • Travels at a constant speed of 3.0 x 108 m/s
  • Electromagnetic Spectrum All the electromagnetic
    radiation form the ES. (fig 4-1, p. 92)

3
Electromagnetic Spectrum
4
Wave Calculations
  • Wavelength (?) - distance between two peaks .
    Measured in meters
  • Frequency (v) - number of peaks that pass a point
    each second.
  • Hz Hertz s-1
  • c ? v       
  • where c 3.0 x 108 m/s

5
Is light really a wave?
  • Max Planck did experiments with light-matter
    interactions where light did not act like a wave
  • Photoelectric Effect - emission of electrons from
    a metal when light shines on the metal.
  • Only emitted at certain energies wave theory
    said any energy should do it.
  • Led to the particle theory of light

6
  • Planck suggested that objects emit energy in
    specific amounts called QUANTA
  • Quantum - minimum quantity of energy that can be
    lost or gained by an atom.
  • led Planck to relate the energy of an electron
    with the frequency of EMR            
  • E hv           
  • E Energy (J, of a quantum of radiation)
  • v frequency of radiation emitted
  • h Plancks constant (6.626 x 10-34 Js)

7
Equation Practice
  • What is the frequency of yellow light with a
    wavelength of 548 nm?

8
Equation Practice
  • What is the wavelength of blue light with a
    frequency of 4.60 x 1023 Hz?

9
Equation Practice
  • What is the energy of magenta light with a
    wavelength of 691 nm?

10
  • leads to Einsteins dual nature of light (EMR
    behaves as both a wave and a particle)
  • Photon - particle of EMR having zero mass and
    carrying a quantum of energy.

11
Hydrogen Emission Spectrum
  • Ground State - Lowest energy state of electron.
  • Excited State - higher energy than ground state.
  • Bright-line Spectrum (emission spectrum)
  • Series of specific light frequencies emitted by
    elements
  • "spectra are the fingerprints of the elements"

12
The Development of A New Atomic Model
  • Rutherfords model was an improvement over
    previous models, but still incomplete.
  • Where exactly are electrons located?
  • What prevented the electrons from being drawn
    into the nucleus?

13
Bohr Model Of H Atom
  • Bohr explained how the electrons stay in the
    cloud instead of slamming into the nucleus
  • Definite orbits paths
  • The greater the distance from the nucleus, the
    greater the energy of an electron in that shell.

14
  • Electrons start in lowest possible level - ground
    state.
  • Absorb energy - become excited and shift upward.
  • Dropping back down - emits photons (packets of
    energies equal to the previously absorbed
    energy).
  • Hydrogen Emission Spectrum

15
Quantum Model of the Atom
  • Bohrs model was great, but it didnt answer the
    question why?
  • Why did electrons have to stay in specific
    orbits?
  • Why couldnt the electrons exist anywhere within
    the electron cloud?
  • Louis de Broglie pointed out that electrons act
    like waves
  • Using Plancks equation (Ehv), dB proved that
    electrons can have specific energies and that
    Bohrs quantized orbits were actually correct

16
Heisenberg Uncertainty Principle
  • Impossible to determine both the exact location
    and velocity of an electron

17
Schrodinger Wave Equation
  • He gave more support to Bohrs quantized energy
    levels
  • Quantum theory describes the wave properties of
    electrons using mathematical equations
  • Disproved Bohrs train tracks within those
    energy levels
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