Foundations Models of the Atom and the Foundations for the Periodic Chart.

Foundations

Models of the Atom and the Foundations for the

Periodic Chart

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The Periodic Table of the Elements Lists All Known Elements in Rows and Columns


Periodic Table Terminology


Discover of Subatomic Particles

• ~1897 J.J. Thompson measured the mass of cathode rays. He found them to be 1800 times lighter than the lightest known element. These were subsequently called electrons.

• ~1932 The development of the mass spectrometer showed integer variations of mass of particles.• The ratio of charge to mass determined the deflection

of an ionized particle in a magnetic field.• It was determined that a “+” charged particle accounted

for the deflection. This was the proton.• The integer mass differences unaffected by the

magnetic field had to be uncharged particles of mass equal to that of the proton. This was the neutron


Having the particles, the question of where were they had to be answered.J.J. Thompson initially proposed the “Plum Pudding” model where the atomic mass was distributed evenly through the atom.

The Structure of the Atom


Rutherford’s Gold Foil Experiment

Rutherford passed alpha particles through an extremely thin gold foil. He found most passed through but occasionally one would be deflected back.

Rutherford Conclusions: All of the mass of the atom is concentrated at the center or “nucleus”.


Schematic Magnified Cross-section of an Atom


Atomic Particle Mass and Change


Color and Energy and Visible Light Form a Continuous Spectrum


Quantum Model and the Failure of Classical Physics

• Around the early 1900’s, many observations were unable to be explained using classical physics• Black body radation• Diffraction of electrons• Line Spectra

• Cumulated observation necessitated a new mechanics to explain them. The result was the birth of Quantum Mechanics


(a) Light From a Hydrogen Lamp When Dispersed by a Prism is Split into its Components (b) The

Emission Spectrum of Hydrogen Consists of Just Four Colors of Visible Light: Red, Green,

Cyan, and Violet (Magenta)


(a) We Can View The Restricted Energy of an Atom as Steps on a Ladder, To the Left of the Ladder Is an Energy-level

Schematic for the Steps (b) The Line Spectrum Relates to the Difference Between the Positions of the Steps, Transition Energies for Five Transitions Ending on Level B are Shown Here as a Line Spectrum Below the Energy-level Schematic


(a) Bohr's Model Shows the Electron Increasingly Far From the Nucleus in Higher-

energy Orbits (b) The Energy of the Electron is Shown in this Energy-level Diagram


1927 Solvay Conference


In the Oscillation of a Drumhead with No Friction, the Drumhead Cycles Indefinitely from a

Crest to Flat to a Trough, and Back Again


Four Successively Higher Energy Modes of a Drum Shown as Surface Plots and Contour Plots, Contour Plots are Similar to

Maps with Elevation Lines

Vibrating Drumhead(You-Tube) mp4


Image of a Copper Surface with a Ring of 48 Iron Atoms, Taken with a Scanning

Tunneling Microscope (STM)IBM Research Center


An s Orbital Is Spherically Symmetric


(a) The 1s Orbital is the Lowest Energy, n=1, State of the Electron (b) The Spherical Surface has been Cut by a Contour to Show the Space-filling Nature of the 1s Electron Wave (c) Looking Down on the Electron Contour Plot Clarifies the Circular Symmetry of the Electron Density (d) A Plot of the Amplitude of the Wave as a Function of the Distance from

the Center of the Sphere Illustrates the Exponential Drop in Density with Distance Away from the Nucleus


The First Excited State of the Electron has One Node, When the Node Is a Spherical Node, the State Consists of Two Large-amplitude Spheres

and Is Called a 2s Orbital


The Node of an Electron Orbital Can Be a Plane that Cuts Through the

Center of the Atom


The Three p Orbitals Illustrated by the Bounding Surface that Contains 90% of the

Electron Wave, Orbitals are Labeled According to their Direction


(a) A px Orbital Shownwith a Slicing Surface

in the x-z Plane (b) The Contour Map Shows the Node in

the y-z Plane (c ) The py and pz Orbitals are

Similar, with Lobes and Nodes Rotated

90 Degrees


Orbitals are represented in Spherical Coordinates


P-orbital equationsProblem 2.85 asks you to show that when the squares of

the probabilities are added, it results in a sphere of probability


The Five 3d Orbitals. The Turquoise and Yellow Lobes are Crests and Troughs, Respectively.

The Labels for These Orbitals Reflect the Directions in which the Quadratic Function

has a Maximum Value


A Plan Slicing Through One of the d Orbitals


Four Quantum Numbers Indicate the Electron Orbital and Spin


(a) Energy Levels in Hydrogen Depend Only on the Shell or Principal Quantum Number, n .(b) In Multi-electron Atoms, as Electrons Occupy Orbitals Nearer to the Nucleus, Outer Electrons are Shielded from the Nuclear Charge

Electron Shielding and Energy Levels


The Ionization Energy of the Three Electrons in the Lithium Atom Demonstrate the Shielding of the Outer-

shell Electron by the Two Inner-shell Electrons


Ionization Energy Jumps After the First Ionization in Group 1, After the Second Ionization in Group

2, and After the Third Ionization in Group 13


Electron Filling Occurs in Blocks in the Periodic Table

Foundations Models of the Atom and the Foundations for the Periodic Chart.

Documents

atomic mass

mass spectrometer

atomic particle mass

integer variations of

level b

restricted energy

mass of cathode rays

steps b