1. (8th) Chapter 4-1 Cornell Notes “Introduction to Atoms”

2. (8th) Chapter 4-1 Cornell Notes Key Questions How did atomic theory develop and change? What is the modern model of the atom?

3. (8th) Chapter 4-1 Cornell Notes Key Terms

5. (8th) Chapter 4-1 Cornell Notes atom: smallest particle of matter; atomic theory grew from models. Paragraph 1

6. (8th) Chapter 4-1 Cornell Notes John Dalton atom model, all alike and different; 1897 J.J. Thomson: discovered electron; 1911 Ernest Rutherford: discovered nucleus, and contained protons); 1913 Niels Bohr: described electrons having E, moving in orbit around nucleus; electron movement depends on E level; later the neutron is added in the nucleus; Final model: nucleus has protons + neutrons, surrounded by electron cloud. Paragraph 2

7. (8th) Chapter 4-1 Cornell Notes protons, neutrons = in mass; electrons much smaller; but take up more space in atom than nucleus. Paragraph 3

8. (8th) Chapter 4-1 Cornell Notes atom of an element same # of protons; atomic number: # of protons; may have different # of neutrons; Isotopes: atoms w/ same # protons, different #of neutrons; isotope identified by “mass number” mass number = #protons + # neutrons; Note: isotopes have different mass #s but react same way chemically. Paragraph 4