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Period: Jan 1, 1000 to
TImespan
Country- Greece
Idea/Experiment- Democritus was the scientist who developed the theory that the world consists of matter which is made up of “invisible particles” called atoms.
Contributed to our understnading of atoms- He discovered that matter consisted of atoms. If it weren’t for this then the chemical elements would not have been found. -
Jun 1, 1000
Democritus
Country: Greece
Idea/Experiment: Democritus was the scientist who developed the theory that the world consists of matter which is made up of “invisible particles” called atoms.
Contributed to our understnading of atoms: He discovered that matter consisted of atoms. If it weren’t for this then the chemical elements would not have been found. -
Newton
Country- England
Idea/Experiment- Law of mechanics which shows that everything moves around no matter how small.
Contributed to our understnading of atoms- This has told us that atoms are made out of small moving particles. -
Dalton
Country:England
Idea/Experiment: Dalton found out that what distinguished one substance from another was the mass. He believed that the element’s chemical properties were found by seeing the size of the atom.
Contribution to our understanding of atoms: This has told us the protons and the atomic weight of the chemical elements. The theory proved that neutrons, electrons and protons exist and make up an atom. -
Stoney
Country: Ireland
Idea/Experiment:He thought of the name electron for the unit of electrical charge in atom.
Contribution to our understanding of atoms: This information led to the founding of the actual particle and its properties. -
Thomson
Country: England
Idea/Experiment: He found that cathode rays could be deflected by an electric field and realized that they have a small amount of negatively charged particles.
Contribution to our understanding of atoms: It helped us find that atoms consisted of particles called electrons which he called ‘corpuscles.’ -
Planck
Country: Germany
Idea/Experiment: Founder of the quantum theory and also did extensive research on the heat theory. That all particles that have energy heat up.
Contribution to our understanding of atoms: This produced the kinetic theory and also showed that all tiny particles warm up and move around more. -
Nagaoka
Country: Japan
Idea/Experiment: He created an analogical model of the atom showing that electrons revolved around a large nucleus like planets do.
Contribution to our understanding of atom: Learned more about the actual placement of the parts of the atom and produced an easier way to explain this. -
Milikan
Country: United States of America
Idea/Experiment: He conducted the oil-drop experiment. He suspended a charged oil drop was between two metal conductors. When the electric current passed through the conductor, he was able to know the electric field.
Contribution to our understanding of atoms: By doing this he created a way to measure the charge on a single electron. -
Rutherford
Country: New Zealand
Idea/Experiment: He found that there is a positive charge inside the nucleus of the atom. He confirmed Nagaoka’s model which Nagaoka and the rest of the world thought was incorrect at the start.
Contribution to our understanding of atoms: This helped find that the positive charge is confined inside the nucleus only and are called protons. Another part of the atom was discovered later. -
Mosely
Country: England
Idea/Experiment: He confirmed that there were no “missing” elements in the periodic table and predicted the other undiscovered elements. He also found through an X-ray experiment that the energy of an X-ray depended upon the nuclear charge of an atom. It created a test of the order of elements.
Contribution to our understanding of atoms: Before Moseley’s law, atomic numbers were just used to number the elements and occasionally increased as the atomic weight did. Moseley gave -
Bohr
Country: Denmark
Idea/Experiment: He created the Bohr Model which showed the nucleus as a positive charge surrounded by concentric circles with electrons.
Contribution to our understanding of atoms: The chemical traits of an atom are found using the number of electrons found in the outer shell of the atom. -
Chadwick
Country: England
Idea/Experiment: He repeated a different method of tracking particle radiation and looked for a particle with the same mass as protons but no charge.
Contribution to our understanding of atoms: He discovered the neutron in an atom. By doing this he helped discover nuclear reactions.
