honors chem atomic model

Aristotle: Everything was made of four elements, fire, water, earth and air

Democrtius: hypothesized atoms, uncuttable bits that hooked together, no one believes him cause the influence of aristotle is too strong

Antoine Lavioser: Carried out experiments where he carefully weighed out reactants before and after and saw that the mass was conserved 

Dalton's Atomic theory: All matter is composed of tiny indivisible particles called atoms. Atoms of the same element are alike, atoms of different elements are different. Compounds are formed when different elements combine in fixed proportions. Chemical reactions rearrange, nothing is created or destroyed 

Problems with Daltons Theory: Only showed the atom, did not show what's inside nor explained charges 

Thompson models: Shell of a positive charge, with negatively charged electrons inside of it. Atoms are neutral overall.

 Cathode Ray Experiment: JJ Thompson used a cathode ray, and emitted electrons from an cathode to an anode. He put a positive plate on top and a negative plate on the bottom, it was deflected upwards towards the positive plate, so the electrons were negative. 

Millkan: Did his oil drop experiment, which added on to JJ Thompsons plum pudding model, found the mass and charge of electrons 

Millkan Oil Drop Experiment: In the experiment, Millikan sprayed tiny oil droplets into a chamber and observed how they moved in an electric field. He found that the oil droplets became charged with electricity when they picked up electrons from the surrounding air. By measuring the motion of the oil droplets in the electric field, Millikan was able to calculate the charge of the individual electrons.

Alpha Particle: positively charged particles 

 Rutherfords Gold Experiment; He shot alpha particles at a gold foil, and then had a detector around it. Most of it went right through the foil, and some bounced back, because it hit something inside the atoms of the foil, which is the nucleus. 

Rutherford atomic Model: Atom is mostly empty space, but there is a positively charged nucleus in the center with positively charged protons inside, electrons scattered.

Problems with rutherford: If there are positive nucleus, and positive protons, they should repel cause like charges repel, so there must be something else. Also charged particles that move around infinitly are going to lose energy and stop 

Chadwick: Mass of atom does not equal mass of protons, something else. Used this using atomic model, discovered neutrons were neutral charge and the same size and weight as protons so it could move it around. 

Atomic line emission spectrum: When voltage is applied and the atoms absorb energy it becomes excited, excited atoms emit energy as light. Energy varies, color varies 

Planetary Model: Bohr discovered electrons orbit around the nucleus, in different level, chadwick added on because he had no nucleus

Excited state: atoms must absorb energy to go from a lower energy level to higher. 

Ground state: energy becomes emitted and goes to a lower energy level