2. Honors Chemistry Chapter 4 The Structure of the Atom

3. Early Theories of Matter Early Theories of Matter Atomic Theory Atomic Theory –Democritus –Dalton

4. Dalton’s Atomic Theory Dalton’s Atomic Theory Based on experimental results Based on experimental results Matter consists of atoms Matter consists of atoms All the atoms of an element are alike All the atoms of an element are alike Atoms of one element differ from atoms of other elements Atoms of one element differ from atoms of other elements Atoms are indestructible and only rearranged during chemical reactions Atoms are indestructible and only rearranged during chemical reactions

5. Atoms can combine in simple, whole- number ratios to form compounds Atoms can combine in simple, whole- number ratios to form compounds Pg. 102 Pg. 102

6. Discovery of the electron Cathode ray tube (Crooke’s tube) Pg. 105 picture Cathode rays –Particles with negative charg e

7. JJ Thompson Used cathode ray tube to determine charge/mass ratio of particles Identified the particles as electrons

8. Robert Millikan Calculated the charge and mass of an electron “Oil drop” experiment Electron carries exactly one unit of negative charge Mass is 1/1840 the mass of a hydrogen atom

9. Each electron carries one unit of negative charge Proposed “plum pudding” model of the atom “chocolate chip cookie” model Electrons stuck in positive “dough”

10. Rutherford’s Gold Foil Experiment pg. 107

12. IMPORTANT RESULTS!!!! New atomic model Atom mostly empty space Tiny, dense central core – nucleus

13. Rutherford's gold foil experiment

15. Contains all the atoms positive charge Volume of space in which the electrons move huge compared to volume of the nucleus

16. Book analogy: If an atom had a diameter of 2 football fields, the nucleus would be the size of a nickel!

17. Don’t you wish you were here right now?

18. WELL YOU’RE NOT – SO PAY ATTENTION!!!!!!!!!!!!!!!!! !!!!

19. Atomic Theory song!!!

20. NUCLEONS – particles located within the nucleus  Protons and neutrons  Protons Positive charge Mass of 1 amu (atomic mass unit)

21. Neutrons –N–N–N–No charge (neutral) –M–M–M–Mass = 1 amu

22. Electrons LLLLocated outside the nucleus in “shells” EEEEach carries one unit of negative charge MMMMass 1/1840 amu PPPPg. 106 chart for subatomic particles

25. Atomic number Number of protons in the nucleus Identifies the atom as an atom of a particular element Determines its position on the Periodic Table Atomic # = #protons = #electrons

26. MASS NUMBER Number of protons + number of neutrons Number of neutrons = mass number – atomic number Isotopes

28. Isotope Notation Pg. 112 Sample and practice

29. Average atomic mass Weighted average of the naturally occurring isotopes of that element Is a decimal because of the existence of isotopes Pg. 114 Table 4.3 Pg. 116-117 #21-24 Video: How to Calculate an Average Atomic Weight. Video: How to Calculate an Average Atomic Weight.

30. Periodic Table Arrangement of elements where the elements are separated into groups bases on a set of repeating properties Can compare properties of elements based on their position on the table

31. Arranged according to increasing atomic number Horizontal rows – periods Vertical columns – groups (families) Elements within a group have similar chemical and physical properties