1. Chapter 5 Atomic Structure and the Periodic Table
5.1
Atoms

2. Image of Lithium Atoms

3. Atom Questions- Answer in your notes.
What do atoms look like?
Describe what atoms are made of?
Why is an image of individual atoms considered such an important breakthrough?
~See top of page 107

4. Early Models of the atom
Democritus (400 BC) proposed that everything is made of particles called atoms.
Proposed this with no scientific experimentation

5. 2000 years later, English schoolteacher John Dalton performed experiments to test his atomic theory.
Based his observations, Dalton formulated hypotheses and theories know as……….

6. Dalton’s Atomic Theory
All elements are composed of tiny indivisible particles called atoms.
Atoms of the same element are identical and different elements are different.
Atoms of different elements combine in whole number ratios.
Reactions occur when atoms are separated, joined or rearranged. However, one element is never changed to another.

7. Atom – smallest particle of element that retains the properties of the element.

8. Section 5.2
Structure of the Nuclear Atom

9. Subatomic Particles Electrons – negatively charged particles
Discovered by JJ Thomson in 1897.
Used a cathode ray tube. Electrons travel from cathode (-) to the anode (+).
Millikan discovered the quantity of charge

10. Cathode Ray Tube

11. Protons and Neutrons
E. Goldstein observed rays traveling opposite to other rays and called these positive particles protons.
1932, Chadwick confirmed the existence of neutrons.
Protons and Neutrons have about an equal mass.

12. Rutherford Gold Foil Experiment

13. Rutherford Gold Foil Experiment
In 1911, Ernest Rutherford shot alpha particles at thin gold foil. Measured reflections on fluorescent screen.
To their surprise most passed on through.
Concluded the atom has a nucleus is the core of the atom and composed of protons and neutrons

14. Atom is mostly empty space!
If the atom were the size of this stadium, the nucleus would be about the size of a marble.