History of Atomic Model • Democritus: • - all things are composed of minute, invisible, and indivisible particles, atoma (indivisibles) in constant motion through otherwise empty space. Kenon • Sir Joseph John Thompson 1900: • analyzed the nature of cathode rays • he reduced that they had particles like properties and were identical regardless of the material producing the rays. • Plum-Pudding Model: • - Lord Kelvin and JJ Thompson concluded that the atom was composed of tiny negatively charged electrons and positive charge mixed together. This was called the Plum-Pudding Model. • Rutherford Gold Foil Experiment 1911: • - Ernst Rutherford shot alpha particle at extremely thin gold foil • - This result was thought to be like cannon balls bouncing off • - Most went right through with little deflection, but some bounced back tissue paper • Rutherford Atomic Model: • -The alpha particle must have bounced off an area of the atom that is positively charged and extremely dense • -Rutherford concluded that the atom has a dense positive nucleus with electrons orbiting around. • Bohr Model 1913 • - Light is emitted from matter at particular energies, or quanta • -Light is produced when electrons moved from high energy atoms to low energy atoms • - Electrons exist at particular orbits • Modern Atomic Model: • - Quantum Mechanism shows how there is a limit to our ability to determine the motion and position of particles • - The motion of objects is described using a wave equation Ψ (PSI), where Ψ is the probability distribution around the hydrogen atom we obtain orbital shapes. • Inside the Nucleus • - the nucleus contains protons and neutrons • - protons and neutrons are composed of quarks • -the strong force between the quarks is what holds the nucleus together. The mechanism is still not well understood.