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John Dalton
John Dalton proposed the Atomic Theory which explained that all matter was composed of small indivisible particles called atoms. He said atoms had unique characteristics and weight for different elements. He also stated that there are three types of atoms: simple, compound, and complex. The simple type of atoms are elements, the simple type are simple molecules, and the complex type are called complex molecules. http://www.biography.com/people/john-dalton-9265201. -
Dalton's Model
Dalton's model was that the atoms were tiny, indivisible, indestructible particles and that each one had a certain mass, size, and chemical behavior that was determined by what kind of element they were. It shows that atoms of different elements combine to form compounds. These compounds are always made up of atoms combined in definite and fixed proportion, which never changed. -
William Crooke
William Crookes built an apparatus, now called a Crookes tube that detected radioactive emissions of elements and verified atomic theory. He discovered cathode rays, which had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass. -
J.J. Thomson
Thomson discovered the electron. His work put forward a new theory, that atom was made up of small particles.Thus, he discovered the electrons. He proved his theory using the cathode ray tube. In 1904 , he proposed a new atomic model called the plum pudding model. It aimed to explain emission lines by assuming electrons were trapped in a continuous blob of positive charge. -
Plum Pudding Atomic Model
It is also known as the Chocolate Chip Cookie or Blueberry Muffin Model. Thomson proposed that the atom was a mass of positive charge with negative electrons embedded into it like raisins in plum pudding. -
Ernest Rutherford
Rutherford published his atomic theory that suggested that most of the mass of the atom is contained in the small nucleus, and that the rest of the atom is mostly empty space. He came to this conclusion following with the famous gold foil experiment, which involved the firing of radioactive particles through thin metal foils and detecting them using screens coated with zinc sulfide. -
Rutherford Model
In this model the electrons and protons are uniformly mixed throughout the atom. It has a very dense positively charged nucleus, with electrons orbiting round the nucleus. This model presented a serious difficulty for the classical theory of electricity and magnetism, which predicts that the electron should spiral into the nucleus in a fraction of a second, radiating electromagnetic energy while doing so. -
Niels Bohr
Bohr developed an explanation of atomic structure that underlies regularities of the periodic table of elements.
The Rutherford model had a major drawback, it could not explain why electrons do not fall into the nucleus by taking a spiral path. So he proposed a model (Bohr's Atomic Model), which gave a new arrangement of electrons in the atom. He argued that electrons could revolve around the nucleus in only 'certain orbits', each orbit having a different radius. -
Bohr's Model
This model, depicts the atom as small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus. It is similar in structure to the solar system. Electrons assume only certain orbits around the nucleus. These orbits are stable and called "stationary" orbits. Each orbit has an energy associated with it. Light is emitted when an electron jumps from a higher orbit to a lower orbit and absorbed when it jumps from a lower to higher orbit. -
Quantum Mechanical Model
Erwin Schrodinger invented it. Of course, Schrodinger built his knowledge on the ideas of former scientists.The Quantum model is the most recent model of the atom. It is based on quantum mechanics (mathematical solutions of theoretical equations). Although it is more difficult to understand than the Bohr model, it can be used to explain observations made on complex atoms. It helps you understand what you observe in nature. -
James Chadwick
James Chadwick proved the exsistence of neutrons. His research greatly increased the understanding of the atomic nucleus. Before his discovery, scientists knew of the existence of protons in the nucleus, but not neutrons. He bombarded the alpha rays on Beryllium atom and observed that it artificially became radioactive for a short time. It emitted material rays containing neutral particles having mass almost equal to proton and proposed the name Neutron for the newly discovered particle.
