4.1 The Development of the Atomic Theory Greek (Democritus) Year: 4th Century BCE Was the atom divisible? Universe is made up of “indivisible” units called atoms. http://www.fordhamprep.org/gcurran/sho/sho/images/democri.gif

Greek Did they do experiments? If so, what did they do? No experiments were done. Made up theories about how the world works. What part of the atom was discovered or any other information about this model? Atoms were in motion which caused the changes in matter that were observed

Greek What did their model of the atom look like? Atoms of liquid were round and smooth. Atoms of solids were rough and prickly. http://reich-chemistry.wikispaces.com/file/view/demo._atom_model.gif/97847685/demo._atom_model.gif

4.1 The Development of the Atomic Theory John Dalton Year: Early 1800’s Was the atom divisible? His theory said all matter is made up of individual particles that could not be divided. http://en.wikipedia.org/wiki/File:Dalton_John_desk.jpg

Dalton Did they do experiments? If so what did they do? His experiments were measuring the masses of elements that combine when the compounds are formed. http://ichef.bbci.co.uk/images/ic/640xn/p01ghrbg.jpg

Dalton What part of the atom was discovered or any other information about this model? Dalton’s Theory: 1. All elements are composed of atoms. 2. All atoms of the same element have the same mass, and atoms of different elements have different masses. 3. Compounds contain atoms of more than one element. 4. In a particular compound, atoms of different elements always combine in the same way.

Dalton Each atom is represented as a tiny, solid What did their model of the atom look like? Each atom is represented as a tiny, solid sphere with a different mass. http://chemistryforum.yolasite.com/resources/DaltonsAtomModels%5B1%5D.jpg

4.1 The Development of the Atomic Theory J.J. Thomson Year: Late 1800’s Was the atom divisible? Thomson’s experiments provided evidence that the atom is made up of smaller particles. http://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/J.J_Thomson.jpg/383px-J.J_Thomson.jpg

Thomson Did they do experiments? If so, what id they do? He was experimenting with electricity, called cathode ray tubes. 1. When the current was on, the disks became charged. 2. A glowing beam appeared in the tube. 3. The charged plates caused the beam to bend. http://www.kentchemistry.com/images/links/atomic/1897_thomson2.jpg

Thomson What part of the atom was discovered or any other information about this mode? 1. The atom overall is neutral. 2. He hypothesized that there was charges evenly scattered throughout the atom. 3. The atom was filled with a positively charged mass of matter. http://withfriendship.com/images/i/40036/card-33-of-56.gif

Thomson What did their model of the atom look like? “Plum-pudding model” similar to a blueberry muffin: the blueberries are the electrons . Or like chocolate chip ice cream: the chocolate chips are the negative electrons in the positive ice cream http://image.wistatutor.com/content/atoms-and-nuclei/plum-pudding-model.jpeg

4.1 The Development of the Atomic Theory Ernest Rutherford Year: Early 1900’s Was the atom divisible? He continued with the theory from Thomson. http://upload.wikimedia.org/wikipedia/commons/thumb/5/5c/Ernest_Rutherford_cropped.jpg/200px-Ernest_Rutherford_cropped.jpg

Rutherford Did they do experiments? If so, what did they do? 1. He discovered that uranium emits fast moving particles that he called alpha particles. 2. He did experiments with those particles and gold foil. 3. He believed that the particles would go straight through. 4. Some of the beams bounced back. http://reichchemistry.wikispaces.com/file/view/Ernest_Rutherford_2.gif/44973665/Ernest_Rutherford_2.gif

Rutherford What part of the atom was discovered or any other information about this model? 1. All of the atom’s positive charge was concentrated in the nucleus. 2. Alpha particles traveled around the nucleus, some coming very close. http://www.daviddarling.info/images/Rutherford_atomic_model.jpg