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History and Structure of the Nuclear Atom

History and Structure of the Nuclear Atom. The Atom. smallest particle of an element that retains all properties of the element. I. Early Models of the Atom. Democritus (460 B.C. – 370 B.C) first to suggest the existence of atoms

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History and Structure of the Nuclear Atom

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  1. History and Structure of the Nuclear Atom

  2. The Atom • smallest particle of an element that retains all properties of the element.

  3. I. Early Models of the Atom • Democritus (460 B.C. – 370 B.C) • first to suggest the existence of atoms • believed atoms were indivisible and indestructible

  4. B. Dalton • Atoms of the same element are identical • Each element is unique • Atoms combine in fixed ratios to form compounds Name of theory Billard Ball Model

  5. C. J.J. Thomson • Discovered electron • Suggested atom looked like plum pudding (or a blueberry muffin or chocolate chip cookie) with electrons evenly distributed throughout positive sphere Name of theory Plum Pudding Model

  6. D. Rutherford • Conducted gold foil experiment

  7. What did Rutherford expect? Gold Foil Experiment Animation and Discussion

  8. What did Rutherford actually see?

  9. D. Rutherford • Conducted gold foil experiment • Proposed atom is mostly empty space • Concluded all positive charge and mass is concentrated in small region called nucleus Name of theory Nuclear atom

  10. D. Rutherford • All the positive charge and all the mass of the atoms was concentrated in a small region called the nucleus • “This is almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you.” – Rutherford, 1938

  11. E. Bohr • depicts the atom as a small, positively charged nucleus • surrounded by electrons that travel in circular orbits around the nucleus Name of theory Planetary Model

  12. F. Schrödinger • model allowed the electron to occupy three-dimensional space like an electron “cloud” • Used a mathematical equation to show a model of electrons as waves Name of theory Quantum Mechanical Model or Electron Cloud Model

  13. A. Size II. More about the Atom • Teeny tiny • observable with instruments such as a scanning tunneling microscope.

  14. B. Parts (called Subatomic Particles) • Protons: p+ • charge = positive +1 • mass =1 • Electrons: e- • charge = negative -1 • mass ~0 • Neutrons: no - charge = zero - mass = 1

  15. C. Location of Parts • Nucleus: center of atom • contains protons and neutrons • has a positive charge • contains almost ALL of the mass of the atom • Outside nucleus: • Contains electrons • Has a negative charge • Occupies almost ALL of the volume of the atom

  16. D. Atomic Charge • Atoms are NEUTRAL • # of protons = # of electrons (ALWAYS if you’re talking about an ATOM)

  17. Fun Facts • The volume of a hydrogen nucleus is a trillion times smaller than the volume of a hydrogen atom, yet the nucleus contains most of the mass. • If the nucleus (proton) of a hydrogen atom were as large as the width of a human thumb, the electron would be on the average about one kilometer away in a great expanse of empty space.

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