Discussion: Three Atomic Models of the Atom Some people believe that theories never change. That isnt true. Theories change until we get it right. The atomic theory is an example. The first atomic theory was named after John Dalton. The atomic theory is at least 3000 years old but John Dalton was the first to develop a modern theory based on scientific evidence. But what did it say? Turn to page 52 Daltons Atomic Theory Elements are made of tiny particles called ___ 2. All atoms of a given element are ________ 3. The atoms of a given element are different from ______ Daltons Atomic Theory 4. Atoms of one element can combine with atoms of other elements to form compounds. 5. Atoms are indivisible in chemical processes. WeberTube - Discovery of the electron Thompsons Model or the Plumb Pudding Model After watching the video on the cathode ray tube, describe the Plumb Pudding model of the atom The Atom Can be Divided The atom contains electrons, protons and neutrons which are called subatomic particles. JJ Thompson discovered the electron. With this discovery, it was known that the atom is divisible and that #5 was wrong. 5. Atoms are indivisible in chemical processes. Rutherfords Gold Foil Experiment Video Rutherfords Model The Setup for the Rutherford Model Lead Box The Atom is Mostly Empty Space The Nucleus A very small very dense core of the atom. It contains positively charged protons and neutrally charged neutrons Protons and Neutrons Protons are positively charged particles in the nucleus. The neutron is also in the nucleus but it has no charge Both the proton and neutron are very dense. Almost all of the mass of the atom is contained in the nucleus. Comparing the mass of an Electron to the Proton Comparing The Mass of an Electron to the mass of a Neutron Proton and Neutron