Jessie Boswell question 1

Examine the history of the development of the atom. We have already discussed the
major players in the development of the atom. Pick out at least 8 major players who
helped aid in the development of the concept of the atom. Then explain each
experiment in a concise explanation. Then explain how each one aided in the
development of the next or how their concept assisted in the further development of the current quantum model of the atom.

Democritus, Dalton, Mendeleev, JJ Thomson, Rutherford, Moseley, Bohr, Chadwick,

Democritus-

Democritus was the type of person to look at the world with mechanistic type of views. Democritus had a theory that everything was made up of atoms and that they could never be destroyed and are always moving around. This is part of what helped Dalton create his theory.

Dalton-

He came up with Dalton’s atomic theory. This theory was partly right by him saying that atoms of the same element are alike in weight and other properties and that different atoms are different in weight and other properties. He was also right about compounds forming by the union or separation of definite numbers of atoms. The incorrect part was that all matter is composed of very small indivisible particles called atoms. Also, that atoms do not divide in chemical reactions; only whole atoms unite with other atoms, this was incorrect. Dalton helped with our quantum model by providing that every atom is different.

Mendeleev- organized the periodic table by the elements atomic weight and properties. Predicted where there was gaps in the periodic table that the element would be found and that it would be put in to the proper place without affecting the order of the table. Mendeleev was right and three elements were found in his lifetime. These elements are lifetimeógallium, scandium, and germanium. This helped with understanding the universe and how things are in the world. Mendeleev helped with Moseley to see that the PT needed to be arranged by atomic number.

JJ Thomson- Used Cathode rays to hypothesize that there were smaller particles contained inside of the atom. JJ was right and the particles inside are called electrons. These are negatively charged particles and are fundamental parts of the atom. The cathode rays are currents of electricity inside of glass tubes. Thomson finding electrons helped with the quantum model because it shows that there are electrons in the outer parts.

Rutherford- Used the gold foil experiment to shot that there are protons in the atom. This experiment used a particle emitter and shot the particles through a slit which then could pass through gold or bounce off of it and back onto the surrounding layer. Rutherford helped with the quantum model by showing that there is positive charged particles, which led to other people drawing the atom and leading up to the quantum atom.

Moseley-

Moseley provided a more accurate PT by arranging the elements by atomic number. Moseley showed that some of the elements did not have the correct atomic masses and that by ordering them by atomic number it helped solve the problem of missing elements. This helped the quantum model by showing how many electrons there truly are.

Bohr- Bohr corrected Rutherford by saying that electrons travel in different orbits around the nucleus. Bohr said that each ring going out could hold more than the inner rings. Bohr also said that these orbits determined the atom’s chemical properties. Bohr helped with the quantum model by showing that there are different electron energy levels and that electrons were in a certain level.

Chadwick-

Chadwick had been working with Rutherford and he thought that there was a neutral part to the atom because the atomic mass did not add up when you looked at the whole atom. Chadwick used a lot of experiments to show that point zero one percent of the neutron was bigger than the proton. The neutron helped to get the atomic mass to finally be equal, and this helped show where to put the neutron because neutrons do not bond with any other particles.