2. Chapter Menu The Structure of the Atom Section 4.1 Early Ideas About Matter Section 4.2 Defining the Atom Section 4.3 How Atoms Differ Section 4.4 Unstable Nuclei and Radioactive Decay Exit Click a hyperlink or folder tab to view the corresponding slides.

4. Section 4-1 Section 4.1 Early Ideas About Matter (cont.) Dalton's atomic theory The ancient Greeks tried to explain matter, but the scientific study of the atom began with John Dalton in the early 1800's.

7. Section 4-1 Greek Philosophers (cont.)

9. Section 4-1 Greek Philosophers (cont.)

12. End of Section 4-1

14. Section 4-2 Section 4.2 Defining the Atom (cont.) atom cathode ray electron nucleus proton neutron An atom is made of a nucleus containing protons and neutrons; electrons move around the nucleus.

32. End of Section 4-2

34. Section 4-3 Section 4.3 How Atoms Differ (cont.) atomic number isotopes mass number The number of protons and the mass number define the type of atom. periodic table: a chart that organizes all known elements into a grid of horizontal rows (periods) and vertical columns (groups or families) arranged by increasing atomic number atomic mass unit (amu) atomic mass

38. Section 4-3 Isotopes and Mass Number (cont.)

43. End of Section 4-3

45. Section 4-4 Section 4.4 Unstable Nuclei and Radioactive Decay (cont.) radioactivity radiation nuclear reaction radioactive decay alpha radiation Unstable atoms emit radiation to gain stability. alpha particle nuclear equation beta radiation beta particle gamma rays

51. Section 4-4 Radioactive Decay (cont.)

56. End of Section 4-4

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90. CIM Table 4.3 Properties of Subatomic Particles Figure 4.12 Rutherford's Experiment Figure 4.14 Features of an Atom Figure 4.21 Types of Radiation

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