1. What elements make up these substances? 1. Sodium (Na) in salt 2. Helium ( He) in balloons 3. Iron ( Fe) in cars. Rust means iron is present. 4. Gold ( Au) in Jewelry. 5. Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe) gases are in signs. 6. Aluminum ( Al)

2. Models of the atom Over the past 1600 years scientist have been observing matter around them. From these observations they were able to start making a picture of what an atom looks like. The story starts about 450 B.C. A greek scolar named Empedocles, came up with the idea of the four elements, earth, air, fire, water.

3. 400 B.C. Democritus suggested that matter was made up of tiny particles called atomos. Which means indivisible.

4. 400B.C. – 1808A.D. Many other scientists supported the idea of the four elements. Robert Boyle 1650: came up with the definition of an element. He tried to prove that air was not an element but a mixture. Joseph Priestley: 1700’s 1 st person to isolate oxygen. Henry Cavendish: isolated hydrogen

5. Models of the atom For each model, make a drawing and write the description for it.

6. Solid Sphere Model John Dalton 1808 Indivisible Solid ( no protons, electrons, neutrons) Looks like a billiard (pool) ball

7. Plum Pudding Model ( Raisin Bun Model) JJ. Thompson 1897 Positive sphere with embedded negative electrons No protons or neutrons

8. Ernest Rutherford 1914 Gold Foil Experiment in Montreal

9. Planetary Model Ernest Rutherford 1914 Small positive center called a nucleus. Surrounded by negative electrons rotating around the nucleus like planets going around the sun No neutrons

10. Bohr Model ( Orbit Model) Neils Bohr 1921 Electrons are organized into different energy levels or orbits at different distances from the nucleus. This model explains why substances behave the way they do.

11. Electron Cloud Model Louis de Broglie and Erwin Schrodinger Electrons rotate around the nucleus in clouds

12. Heisenberg The Heisenberg uncertainty principle He said that it is impossible to predict exactly where an electron will be at any given time.