Unit 1: Structure of Atoms and Elements Mrs. Collins' Physical Science Atomic Model History Unit 1: Structure of Atoms and Elements Mrs. Collins' Physical Science
Dalton's Model Based on ancient Greek model States the following All matter is composed of extremely small particles called atoms. Atoms of a given element are identical in size, mass, and other properties. Atoms of different elements differ in size, mass, and other properties. Atoms cannot be subdivided, created, or destroyed. Atoms of different elements can combine in simple whole number ratios to form chemical compounds. In chemical reactions, atoms are combined, separated, or rearranged.
JJ Thompson's Model Discovered the electron in 1897 Whoa.... there are smaller parts of an atom? Dalton's theory no longer valid 1904 - "Plum Pudding" model no concept of nucleus at this time. Believed electrons floated in "soup" of positive charge like plums in a pudding. Still no concept of how electrons arranged.
Rutherford Model 1900 - used radiation to find positively charged particles in atom Because of the experiment, determined must be a dense, positive ball at center Negative particles surround the positive ball
Bohr Model Proposed that electrons can only orbit nucleus have specific orbits known as "Planetary Model"
Chadwick Model 1932 - Chadwick discovered neutron in nucleus neutral chage adds mass Because of discovery of neutrons about the same size of protons... new measurement unit created atomic mass unit (AMU) protons and neutrons have AMU of 1