2. Page 23 of your notebook

3.  Summarize the observed properties of cathode rays that led to the discovery of the electron.  Summarize the experiment carried out by Rutherford and his co-workers that led to the discovery of the nucleus.  List the properties of protons, neutrons and electrons.  Define atom and isotope.

4.  Very small  1 x 10 22 atoms in 1 penny  Equivalent to 1 grain of sand in a sandbox the size of Texas

5.  Smallest characteristic of a given element  Make up everything  Different for each element  Only 90 elements occur in nature

6.  Too small to see with an ordinary microscope  Need scanning tunneling microscope to get an image of an atom  Tells nothing about the structure of an atom

7.  Atoms in Kanji, they spell "atom" using iron atoms on a copper surface. The literal translation is something like "original child."

8.  Only 4 elements  Fire (red)  Water (blue)  Air (grey)  Earth (brown)

9.  Democritus postulated tiny particles of water that could not be subdivided further  Called them atomos (means indivisible)

10.  Thought everything was continuous  Atoms didn’t exist  Ancient Greeks could not test either model  This view prevailed for >2000 years

11.  By the 1790’s, the study of matter was revolutionized by the analysis of chemical reactions  Beginning of technology  This lead to the discovery of several basic laws

12. Father of Modern Chemistry law of conservation of matter (mass): The total mass of substances does not change during a chemical reaction. reactant 1 + reactant 2 total mass product total mass= iron + oxygeniron(III) oxide Fe + O 2 Fe 2 O 3 70.0 g + 30.0 g100.0 g Antoine Lavoisier (1743-1794)

13.  Accurately weighed starting materials and products of reactions

14.  Mass is neither created nor destroyed during chemical reactions  Cannot create material out of thin air  Make new materials by rearranging atoms  Basis for chemical calculations

15. 1. All matter is composed of extremely small particles  Atoms are indivisible 2. Atoms of a given element are alike but different from atoms of any other element  Atoms for any element have identical chemical and physical properties 1803 John Dalton:

16. 3. Atoms can not be subdivided, created or destroyed. 4. Compounds are formed when different elements combine in fixed proportions ▪ Typically written with smallest whole numbers - Law of Definite Proportions - Law of Multiple Proportions 1803 John Dalton:

17. 5. A chemical reaction involves combining, separating or rearranging of atoms Law of Conservation of Mass 1803 John Dalton:

18.  Modern Atomic Theory proved a few of Daltons ideas where wrong.  Atoms are divisible into smaller particles ▪ Electrons, neutrons and protons  A given element can have atoms with different masses ▪ Isotopes

19. Cathode rays – The ray of light emitted by the cathode (negative electrode) in a glass discharge tube; travels in straight lines, unless deflected by magnetic or electric fields.

20. Studied cathode rays and determined that J. J. Thomson (1897) Atoms are divisible into even smaller particles.

21. Millikan’s Oil-Drop Experiment Determined the negative charge of an electron

22. James Chadwick Discovered a particle in the nucleus that had no charge neutron

23.  Studied the glow caused by the cathode ray tube  Chemically treated paper that glowed ▪ Even through walls!

24.  Becquerel found that uranium ores would fog photographic plates in the dark

25.  Marie and Pierre Curie isolated 1/30 ounce of radium from one ton of uranium ore. Marie died from radiation-induced leukemia. The pages of her lab notebook were later found to be contaminated with radioactive fingerprints.

26.  – spontaneous emission of radiation from certain unstable elements

29. Rutherford’s  -Scattering Experiment (Gold Foil) and Discovery of the Atomic Nucleus The vast majority of an atom’s volume is empty space. Nucleus - The tiny central region of the atom that contains the positive charge and essentially all the mass.

30.  Rutherford suggested:  Most of mass in nucleus  All the positive charge  Nucleus: protons and neutrons  Neutrons have mass but no charge  Very small size compared to the rest of the atom  The rest of the atom contains the electrons

31.  Particles smaller than the atom  Number of protons in element = atomic number  Element: all atoms having the same atomic number

33.  Atoms having the same atomic number BUT differing in number of neutrons

34. Z AXAX A = mass number = number of protons + number of neutrons = number of nucleons Z = atomic number X – symbol of the element Isotopes of hydrogen

35. A Neutron walked into a bar and asked how much for a drink. The bartender replied, “for you…. no charge.” - Jaime- Internet Chemistry Jokes