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John Dalton
Discovery - Atomic Theory: elements are made up of atoms; atoms of a given element are identical in properties; atoms can't be subdivided, creased, or destroyed; atoms of different elements combine in whole number ratios; in chemical reactions, atoms are combined, seperated, or destroyed.
The law of definite proportions: any sample of a compound always has the same composition.
The law of conservation of mass: mass of the products of a recation equals the mass of the reactants. -
John Dalton
The law of multiple proportians: the mass ratio for one of the elements in a compound that combines with a fixed mass of another element can be expressed in small whole numbers.
Title/Description of Experiment- he created a "Table of Atomic Weights" and used the iformation from this table to place the elements in a significant order determined by the weight of the elements. He compared the elements' weights to hydrogen, whcih is the lightest element. -
John Dalton
Shortcomings Addressed- He didn't include anything about subatomic particles. No mention of electrons, protons, or neutrons.
Model- Solid Sphere Model -
J.J. Thomson part 2
Title/Description of Experiment-He estimated the mass of cathode rays by measuring the heat generated when the rays hit a thermal junction and comparing this with the magnetic deflection of the rays. His experiments suggested not only that cathode rays were over 1000 times lighter than the hydrogen atom, but also that their mass was the same whatever type of atom they came from. He concluded that the rays were composed negatively charged particles which were a universal building block of atoms. -
J.J. Thomson
Shortcomings addressed- He did not learn about the nucleus of the atom
Model- Plum pudding model -
J.J. Thomson part 1
Discovery: He found that the atom was made up of electrons (subatomic particles) which are 1000 times smaller than the atoms themselves. his discovery that Lenard rays could travel much further through air than expected for an atom-sized particle. He estimated the mass of cathode rays and compared this with the magnetic deflection of the rays. His experiments stated that cathode rays were over 1000 times lighter than the hydrogen atom. He concluded that the rays were composed of very light, -
Ernest Rutherford part 1
Discovery- He discovered that a very small positively charged nucleus, containing much of the atom's mass, was orbited by low-mass electrons.
Experiment- He used the gold foil experiemt to find the nucleaus showed in the picture
Model- nucleaur atomic model
Shortcomings- did not know that the electrons orbited the nucleaus -
Niels Bohr part 1
Discovery- he discovered that the electrons orbited the nucleaus and had electrostatic forces providing attraction between the electrons an the nucleaus.
Experiment- Bohr could determine the energy spacing between levels using rule 3 and come to an exactly correct quantum rule: the angular momentum L is restricted to be an integer multiple of a fixed unit. Once an electron is in this lowest orbit, it can get no closer to the proton. -
Niels Bohr part 2
Model- Plantetary Model
Shortcomings- gives an incorrect value for the ground state orbital angular momentum. The angular momentum in the true ground state is known to be zero.
