The History of Atomic Theory and Subatomic Particles

Quantum Mechanical Model Orbitals Nucleus: Protons + Neutrons Electrons

The Proton  Positively charged.  Located in the nucleus.  Mass equal to the mass of a neutron.  Discovered by Eugen Goldstein (1886) Eugen Goldstein (1886)

The Neutron  Neutrally charged.  Located in the nucleus.  Mass equal to the mass of a proton.  Discovered by James Chadwick (1932) James Chadwick (1932)

The Electron  Negatively charged.  Located orbiting around the nucleus.  Mass approximately 1/1837 the mass of a proton. 1/1837 the mass of a proton.  Discovered by J. J. Thomson (1897) J. J. Thomson (1897)

Early Atomic Theory  The theory of Democritus and Leucippus (his teacher) held that everything is composed of "atoms", which are physically, but not geometrically, indivisible; that between atoms, there lies empty space; that atoms are indestructible; have always been, and always will be, in motion; that there are an infinite number of atoms, and kinds of atoms, which differ in shape, and size.  This theory was based on the idea of taking a sample of a substance and breaking it in half, and then in half again repeatedly until one reached the most basic form of that substance that could not be divided or split any further. The term “Atomos” (which directly translates into “not cutting” or “unable to cut”) was used to describe this.

Development of the Atomic Model  J Dalton  “Billiard Ball or Solid Sphere” Model

Dalton’s Atomic Theory 1.All matter is made of indivisible and indestructible atoms. 2.Atoms of a given element are identical in their physical and chemical properties. 3.Atoms of different elements have different physical and chemical properties. 4.Atoms of different elements combine in simple, whole number ratios to form chemical compounds. 5.Atoms cannot be subdivided, created or destroyed when they are combined, separated, or rearranged in chemical compounds.

Development of the Atomic Model  J. J. Thomson  “Plum Pudding or Raisin Bun” Model

J.J Thomson

The Cathode Ray Tube  Thomson used a Cathode Ray Tube (CRT) to prove the existence of a negatively charged subatomic particle later named the electron.

The Discovery of the Electron  Cathode Ray Tube experiment Cathode Ray Tube experiment Cathode Ray Tube experiment

Development of the Atomic Model  E. Rutherford  “Planetary Model or Nuclear” Model

The Discovery of the Nucleus  Rutherford's Gold Foil Experiment Rutherford's Gold Foil Experiment Rutherford's Gold Foil Experiment

First Conclusion

Second Conclusion

Development of the Atomic Model  N. Bohr  “Bohr or Orbit” Model

Quantum Theory  Max Planck  Albert Einstein  The Photoelectric Effect Effect  The Photoelectric Effect and Photoelectric Cell The Photoelectric Effect and Photoelectric Cell The Photoelectric Effect and Photoelectric Cell

Development of the Atomic Model  Erwin Schrodinger – 1926  “Electron Cloud or Quantum Mechanical” Model Model

Subatomic Particles are Composed of “Quarks”

Atomic Structure  Atomic Number: the # of Protons. the # of Protons.  Atomic Mass: the average mass of all isotopes. This is the number that appears on the periodic table. the average mass of all isotopes. This is the number that appears on the periodic table.  M ass Number : the # of Protons & the # of Protons & Neutrons in an atom. Neutrons in an atom.

Calculating # of P, N & E  # Protons = Atomic Number  # Electrons = Atomic Number in atom (atoms are neutral therefore the # of positively charged protons must equal the # of negatively charged electrons) (atoms are neutral therefore the # of positively charged protons must equal the # of negatively charged electrons)  Mass Number = # Protons + # Neutrons  # Neutrons = Mass Number minus Atomic Number

 Al # P ____ # E ____ # N ____  Fe # P ____ # E ____ # N ____ Atomic Symbols

Show the mass number and atomic number Show the mass number and atomic number Give the symbol of the element Give the symbol of the element mass number 23 Na sodium Na sodium-23 atomic number 11 atomic number 11 Atomic Symbols

Isotopes Atoms with the same number of Protons, but different numbers of Neutrons. Atoms with the same number of Protons, but different numbers of Neutrons. Atoms of the same element (same atomic number) with different mass numbers Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine Isotopes of chlorine 35 Cl 37 Cl 1717 chlorine - 35 chlorine - 37 chlorine - 35 chlorine - 37

Isotopes and Notation