Chapter 4: Guided Notes Name _______________________________________ Topic: Structure of an Atom (pg. 105-109) 1. What is an atom? a. Model of a Boron atom 2. Dalton’s Atomic Theory All elements are made up of tiny indivisible particles Atoms of the same element are identical. Atoms of different elements can mix to form compounds in simple whole # ratios Chemical reactions occur when atoms are separated and rearrange. 3. How small is an atom? If you placed 100,000,000 copper atoms side-by-side, the line would be 1 cm long. 4. Is it possible to observe atoms? Topic: Who were the early investigators of atoms and what did they discover? 5. J.J.Thompson (1897) 6. Robert Millikan (1916) • Discovered the quantity of charge of an electron: • An electron has: • An electron’s mass is _____________ the mass of one hydrogen atom (actual mass: 7. E. Goldstein (1886):