1. Chapter 11 Section 1 Development of the Atomic Theory
History of the Atom
Chapter 11
Section 1
Development of the Atomic Theory

2. Half Full or Half Empty? Completely Full of Matter! Half full of water
Half full of air

3. Reminder… matter - anything that has mass and takes up space
matter is NOT…
Light, Heat, Emotions, Thoughts, & Ideas
Matter is made up of
atoms – the smallest particles into which an element can be divided and will remain the same substance
make up elements
often called the building blocks of matter

4. Think…
Suppose you cut wood into smaller and smaller pieces. Do the small pieces seem to be made of the same matter as the large chunk you started with?

5. History of Matter Democritus (460 B.C. – 370 B.C.) Greek Philosopher
Thought the universe was made of empty space and tiny bits of stuff which could not be divided into smaller pieces
Named these tiny pieces atoms (Greek word atomos “indivisible: cannot be divided”)
Atoms were hard, small particles
Believed different types of atoms existed for every type of matter and came in different shapes/sizes
Ideas were not accepted for nearly 2000 years!

6. To learn more about something in science that is too small to be seen, scientist create…..
MODELS 

7. History of the Atom John Dalton (Early 1800’s)
Schoolteacher and Chemist
Atomic Model (Atomic Theory of Matter)
Set of Ideas (idea model not physical model)
All substances are made of atoms
Atoms are small particles that cannot be created, divided, or destroyed
Atoms of the same element are exactly alike
Atoms join with other atoms to make new substances

8. History of the Atom J.J. Thomson (Late 1800’s to Early 1900’s)
English Scientist
Discovered Electrons
Cathode Ray Tube Experiment
Atoms were not too tiny to divide

9. History of the Atom… J.J. Thomson (Late 1800’s to Early 1900’s)
Atomic Model
Ball of positive charge with electrons embedded in it

10. History of the Atom Rutherford (Early 1900’s)
British Chemist and Physicist
Discovered the Nucleus & the Proton (Gold Foil)
Model of Atom
Electrons were scattered in the empty space around the positively charged nucleus.

11. History of the Atom James Chadwick (1930’s) Student of Rutherford’s
Discovered Neutrons: Ran further experiments using the results of the Gold Foil Experiment
Found that the particles were heavier because of Neutrons
Atomic Model: Proton – Neutron Center

12. History of the Atom Niels Bohr (Early 1900’s)
Discovered Electron Energy Levels
Electrons can jump paths/levels

13. Current Model Electron movement is not completely certain
Electrons stay in the energy levels of the electron cloud