Questions to answer: 1) What were the ancient elements? 2) What scientist ‘discovered the atom’? How did he come up with this theory (you may need to do some internet research to answer this question.) 3) What are the 4 parts to Dalton’s Atomic Theory? 4) Which part of his theory was later proved wrong, and why? 5) What was JJ Thompson’s contribution to the atomic theory? 6) What was Ernest Rutherford’s contribution to the atomic theory? 7) Which model is more accurate, the plum pudding model, or the electron cloud model?

The Structure of the Atom and the Periodic Table Chapters 4 and 5

Atomic Theories- Ancient Ancient Civilizations identified 4 elements: Fire Water Wind Earth The elements could be converted into each other through a cycle end

Atomic Theories- Modern John Dalton Father of modern atomic theory Studied the behavior of gases In all samples of the same substance, the ratio of the elements was always the same end

Atomic Theories- Modern Dalton's Atomic Theory: All elements are made of atoms Atoms of the same element have the same mass This was later proved wrong- Isotopes Atoms of different elements have different masses Atoms combine in whole number ratios You can't have half of an atom Dalton's Atoms Dalton went back to Democritus' view. All matter is made up of individual particles called atoms, which cannot be divided Atoms are little spheres Like marbles

Atomic Theories- Modern J. J. Thomson Performed cathode ray tube experiments Discovered the electron When a magnetic field was applied the beam went toward the positive plate When electricity moves through a gas it produces a glowing beam (neon signs) end

Atomic Theories- Modern Thomson came up with a new model of the atom to explain his results: The Plum Pudding Model Large area of positive charge Small packets of negative charge Think: Chocolate Chip Cookies end

Atomic Theories- Modern Ernest Rutherford: Proved the Plum Pudding Model was wrong! Rutherford came up with a new model of an atom, the electron cloud model: A small, dense, positive nucleus Electrons are outside the nucleus Atoms are mostly empty space Electrons are somewhere in this area + Nucleus