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ATOMIC AND ELECTRONIC STRUCTURE

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Title: ATOMIC AND ELECTRONIC STRUCTURE


1
ATOMIC AND ELECTRONIC STRUCTURE
  • ? fundamentals of the particles ? quantum theory
    and electronic configuration ? the modern
    periodic table ?

2
Historical Background
  • 5 BC - Democritus
  • matter consists of very small,indivisible
    particles Atomos (uncuttable, indivisible)
  • 1799 Joseph Louis Proust
  • law of definite proportion and multiple
    proportions
  • 1808 John Dalton
  • modern atomic theory

3
Historical Background
4
Daltons Atomic Theory
5
Daltons Atomic Theory
6
Discovery of the Atomic Structure
  • The Electron
  • the Cathode Ray Tube

7
Discovery of the Atomic Structure
  • The Electron
  • Joseph John Thomson
  • Electron Mass Charge Ratio 1.76 x 108 C/g

8
Discovery of the Atomic Structure
  • The Electron
  • Robert Millikan
  • Electron Mass 9.10939 x 10-28 g

9
Discovery of the Atomic Structure
  • The Proton
  • Radioactivity

10
Discovery of the Atomic Structure
  • The Proton
  • Ernest Rutherford Alpha-Scattering Experiment

11
Discovery of the Atomic Structure
  • The Proton
  • Nuclear Atom
  • most of the mass of the atom an all of its
    positive charge reside in a very small, extremely
    dense region nucleus
  • most of the total volume of the atom is empty
    space in which electrons move around the nucleus

12
Discovery of the Atomic Structure
  • The Neutron
  • James Chadwick
  • bombarded a thin sheet of beryllium with ?
    particles
  • a very high-energy radiation, similar to ? rays,
    was emitted

13
Discovery of the Atomic Structure
  • The Nuclear Atom

14
Discovery of the Atomic Structure
  • The Subatomic Particles
  • Atomic Mass Unit, amu
  • 1 amu 1.66054 x 10-24 g
  • 1 g 6.02214 x 1023 amu

15
Mass Properties of Atoms
  • Atomic Number, Z
  • gives the charge of the atom
  • Mass Number, A
  • gives the relative mass of the atom
  • Z atomic number
  • p number of protons
  • e number of electrons

Z p e-
  • A mass number
  • p number of protons
  • n number of neutrons

A p n
16
Mass Properties of Atoms
  • Isotopes
  • atoms of a given element that differ in the
    number of neutrons, and consequently, in mass
  • Nuclide
  • an atom of a specific isotope
  • way of denoting an element

ZXA
17
Mass Properties of Atoms
1H1
1H2
1H3
18
Mass Properties of Atoms
  • Atomic Mass Unit, amu
  • exactly equal to one-twelfth the mass of one
    carbon-12 atom
  • Average Atomic Mass / Atomic Weight

mass of one carbon-12 atom
1 amu
AW ?fractional abundance x isotopic weight
19
Properties of Waves
  • Wavelength, ?
  • distance between successive peaks or troughs
  • Cycle
  • complete wavelengths
  • Frequency, ?
  • number of cycles that pass a given point each
    second
  • Amplitude
  • maximum oscillation of a wave

c ? ?
  • c speed of light
  • c 3.0 x 108 m/s

20
Properties of Waves
  • Electromagnetic Radiation

21
Quantized Energy and Photons
  • Christian Huygens
  • light, like sound, is a wave motion
  • Isaac Newton
  • light is made up of very fast and very small
    particles which travel in straight lines
  • sunlight is composed of various color components
    that can be recombined to produce white light
  • Max Planck
  • atoms and molecules could emit (or absorb)
    energy only in discrete quantities

22
Quantized Energy and Photons
  • Quantum
  • fixed amount
  • smallest quantity of energy that can be emitted
    or absorbed as electromagnetic radiation

E h?
  • E energy emitted or absorbed
  • h Plancks constant
  • ? frequency
  • h 6.63 x 10-34 J-s

23
Quantized Energy and Photons
  • Albert Einstein
  • light travel in packets called Photons

Energy of a photon E h?
24
Bohrs Model of the Hydrogen Atom
  • Spectrum
  • produced when radiation containing many different
    wavelength components is separated
  • Continuous Spectrum
  • spectrum consisting of a continuous range of
    colors (i.e., rainbow)

25
Bohrs Model of the Hydrogen Atom
  • Line Spectrum
  • spectrum containing radiation of only specific
    wavelengths

26
Bohrs Model of the Hydrogen Atom
  • Atomic Spectrum

27
Bohrs Model of the Hydrogen Atom
  • Johann Balmer
  • fitted the wavelengths of the four lines of
    hydrogen into a simple formula
  • Rydberg Equation
  • ? wavelength of the spectral line
  • RH Rydberg constant
  • n positive integers
  • RH 1.096776 x 107 /m

28
Bohrs Model of the Hydrogen Atom
  • Neils Bohr
  • Only orbits of certain radii, corresponding to
    certain definite energies, are permitted for
    electrons in an atom.
  • An electron in a permitted orbit has a specific
    energy and is in an allowed energy state. An
    electron in an allowed energy state will not
    radiate energy and therefore will not spiral into
    the nucleus.
  • Energy is only emitted or absorbed by an electron
    as it changes from one allowed energy state to
    another. This energy is emitted or absorbed as a
    photon, E m?.

n 3
29
Bohrs Model of the Hydrogen Atom
  • E energy
  • RH Rydberg constant
  • n quantum number
  • RH 2.18 x 10-18 J

30
Wave Behavior of Matter
  • ? wavelength
  • h Plancks constant
  • m? momentum
  • mass x velocity

31
Wave Behavior of Matter
32
Quantum Mechanics
  • Schrodinger Equation
  • incorporates both the wavelike and particle-like
    behavior of the electron.
  • Orbital
  • describes a specific distribution of electron
    density in space

33
Quantum Mechanics
  • Quantum Numbers
  • describe the distribution of electrons in atoms
  • derived from the mathematical solution of the
    Schrodinger equation for the hydrogen atom
  • describe the atomic orbitals and label the
    electrons that reside in them

34
Quantum Mechanics
  • Principal Quantum Number, n
  • relates to the average distance of the electron
    from the nucleus in a particular orbit
  • determines the energy of the orbital
  • referred to as the shell
  • values 1, 2, 3
  • Angular Quantum Number, l
  • describes the way the electron moves around the
    nucleus
  • shape of the probability distribution
  • referred to as the subshell
  • values 0 to (n 1)

35
Quantum Mechanics
  • S orbital

36
Quantum Mechanics
  • P orbital

37
Quantum Mechanics
  • D orbital

38
Quantum Mechanics
  • Magnetic Quantum Number, ml
  • describes the orientation of the orbital in space
  • values -l to l
  • Electron Spin Quantum Number, ms
  • describes the spin of the electron
  • values ½ , -½

39
Quantum Mechanics
  • Summary
  • n shell number of subshells n
  • l subshell number of orbitals 2l 1
  • n shell number of orbitals n2

40
Electronic Configuration
  • arrangement of electrons in an atom
  • ex Ca 20 electrons
  • Orbital Method
  • 1s2 2s2 2p6 3s2 3p6 4s2
  • Shell Method

41
Electronic Configuration
  • Arrow Method
  • Core Method
  • Ar 4s2

42
Electronic Configuration
43
Electronic Configuration
  • Paramagnetic Substance
  • slightly attracted by a magnet
  • Diamagnetic Substance
  • slightly repelled by a magnet

44
Electronic Configuration
45
Electronic Configuration
  • Valence Electrons
  • electrons in the outermost shell
  • Lewis Dot Notation
  • consists of the symbol of the element and one dot
    for each valence electron in an atom of the
    element
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