1. Atoms and Atomic Theory Essential Questions: How and why has the Atomic Theory changed over time? How can we describe the molecular motion of the states of matter?

2. Atomic Theory Changes over time…

3. 0B0B ecause we can not see atoms, we use models to teach and learn about atoms. 0T0T he atomic theory has changed over time as new technologies have become available. 0R0R emember: Scientific knowledge builds on past research and experimentation.

4. Atomic Theory Timeline ScientistInformationModel John Dalton All matter is made of atoms. Atoms are too small to see, indivisible and indestructible. All atoms of a given element are identical.

5. ScientistInformationModel J.J Thompson Discovered the negative electron, and predicted that there also must be a positive particle to hold the electrons in place. Atomic Theory Timeline

6. ScientistInformationModel Ernest Rutherford Discovered the nucleus of an atom and named the positive particles in the nucleus “protons”. Concluded that electrons are scattered in empty space around the nucleus. Atomic Theory Timeline

7. ScientistInformationModel James Chadwick Discovered that neutrons were also located in the nucleus of an atoms and that they contain no charge. Atomic Theory Timeline Neutrons

8. Atomic Theory Timeline ScientistInformationModel Neils Bohr Concluded that electrons are located in planet-like orbits around the nucleus in certain energy levels.