Atom Lab Extra Credit Who Am I? 1. _______________________ I discovered the electron. I proposed that tiny negative charges were held in a positive cloud much like bits of plum in plum pudding. 2. _______________________ I was the early Greek philosopher who first proposed that all materials were made of atoms. I gave atoms their Greek name – atomos. 3. _______________________ I was the first to propose that electrons orbited the nucleus where the positive charge was located. 4. _______________________ I was an English scientist who first proposed that each chemical element had its own atoms that differed from each other in mass (weight). 5. _______________________ I discovered radioactivity. 6. _______________________ I found that electrons orbit the nucleus in fixed energy levels. I discovered that energy was given off when electron “fell” from a higher energy level to a lower one. Draw and label an isotope of lithium.