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John Dalton William Crookes J.J. Thomson Ernest Rutherford

John Dalton William Crookes J.J. Thomson Ernest Rutherford. Early Theories About ATOMS. 4 Materials:. ATOMS. (2500 years ago). -Earth -Fire -Air -Water. Ancient Greeks-. -Ex. Wood= Earth+Fire. Early Theories About ATOMS. “Cannot be divided” solid spheres-

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John Dalton William Crookes J.J. Thomson Ernest Rutherford

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  1. John DaltonWilliam CrookesJ.J. ThomsonErnest Rutherford

  2. Early Theories About ATOMS 4 Materials: ATOMS (2500 years ago) -Earth -Fire -Air -Water Ancient Greeks- -Ex. Wood= Earth+Fire

  3. Early Theories About ATOMS “Cannot be divided” solid spheres- (No one believed him) (930 BC) Democritus(Greek thinker) – All matter is made up of Atoms

  4. 1808 John Dalton Proved that matter is made up of Atoms Different elements have different masses

  5. (By putting substances together to form new substances and taking them apart chemists discovered that ALL matter is made of elements) 1808 - John Dalton Element – matter made of atoms of only one kind (periodic table of elements)

  6. 1870 - William Crookes Used a cathode ray tube to show streams of particles

  7. (opposite side) 1897 - J.J. Thomson Plum Pudding model Discovered the Electron Bent Crookes stream with a magnet did this with many gases and many elements http://www.aip.org/history/electron/jjsound.htm

  8. Used by modern scientists 1911 - Ernest Rutherford The Nuclear Atomic Model

  9. 1911 - Ernest Rutherford • protons & neutrons • positive charge The Nucleus – the small central core of an atom where most of the mass is located • (electrons found in a cloud around it)

  10. Electron Cloud - Region around the nucleus in which the electrons travel Dalton Thomson Rutherford

  11. Dalton Thomson Rutherford

  12. Particle charge found Electron - negative outside nucleus Atomic Particles- Proton + positive inside nucleus Neutron No charge inside nucleus The basic building blocks of atoms Proton Protons = electrons neutral atom Neutron Electron

  13. VERY SMALL!! Atomic Mass Unit (u) – A unit used to express the masses of atomic particles and atoms (1u=1.66 x 10-27Kg) Size of Atomic Particles- Sooooo small that scientists use: Electron 0 u (1/1836) Proton 1 u Neutron 1 u (1837/1836)

  14. Ex. Stars, Atoms Scientific Models - -Used when objects can’t be studied directly • Many experiments • (how do atoms behave under different conditions)

  15. Element #of protons # of electrons Hydrogen 1 Oxygen 8 Sulfur 16 Gold 79 1 8 16 79 Atomic Number - The number of protons in the nucleus of an atom In a normal atom positive charges (proton) cancel out negative charges (electrons)

  16. Electrons in motion 1913 –Niels Bohr – electrons can follow only certain orbits

  17. Electron Arrangement Ex. He + Energy Level – A region around an atomic nucleus in which electrons move Ex. C Nucleus 2 8 18 32 +

  18. Symbols of Elements - Berzelius (Swedish Scientist) 1st letter – ALWAYS CAPITALIZED 2nd letter(if there is one) – ALWAYS lower case Atomic Symbol – 1 or 2 letters used to represent an atom of an element - Based on the element name (sometimes the Latin name)

  19. The Periodic Table of Elements

  20. Name of Element Atomic Number Symbol Atomic Mass Symbols of Elements Hydrogen 1 H 1.008

  21. Protons = Electrons Mass Number = Protons + Neutrons Mass Number – The sum of the protons and Neutrons in an atom The Number of Particles in a Nucleus (different atoms have different mass #’s)

  22. 4 3 5 11 5 14 7 7 3 10 10 10

  23. Isotopes- Atoms whose nuclei contain the same # of protons, but different #s of Neutrons Ex. Hydrogen-1, Hydrogen-2, Hydrogen-3 (deuterium) (tritium) + + +

  24. Atomic Mass- The average of all the masses of the isotopes of a particular element -Round to the nearest whole #= Mass #

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