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460
Demacratus
The Democritus Atomic Theory revolves around the atoms that are present in the atmosphere. These are about the atoms that are present in all the forms of existence; for instance, solid or liquid. The theory states that these atoms are all individually created and cannot be separated, no matter what scientific. This procedures are applied. The Democritus Atomic Theory is pretty much clear and the ideas are portrayed in manner that can be easily understood. This theory was brought up in 460 BC. -
Antoine Lavoisier
Antoine Lavoisier proved the law of conservation of mass around the year 1789. The law of conservation of mass states that: Mass cannot be created or destroyed.The mass of the reactants must equal the mass of the products. He also proved that oxygen and hydrogen when combined form water. -
Law Of Conservation Of Mass
Established in 1789 by French Chemist Antoine Lavoisier States that mass is neither created nor destroyed in any ordinary chemical reaction. Or more simply, the mass of substances produced (products) by a chemical reaction is always equal to the mass of the reacting substances (reactants). -
John Dalton
He stated his theory in a lecture to the Royal Institution in 1803. All matter is composed of atoms. Atoms cannot be made or destroyed. All atoms of the same element are identical. Different elements have different types of atoms. Chemical reactions occur when atoms are rearranged. Compounds are formed from atoms of the constituent elements. -
Daltons Atomic theory
All matter is composed of atoms. Atoms cannot be made or destroyed. All atoms of the same element are identical. Different elements have different types of atoms. Chemical reactions occur when atoms are rearranged. Compounds are formed from atoms of the constituent elements. -
Demitri Mendeleev
n the late 1860's, Mendeleev began working on his great achievement: the periodic table of the elements. By arranging all of the 63 elements then known by their atomic weights, he managed to organize them into groups possessing similar properties. -
J.J Thompson
Thomson discovered the electron in the year 1897. His work put forward a new theory, that atom was made up of small particles. He proved his theory using the cathode ray tube. -
Cathode Ray Tube
A cathode is a terminal or electrode at which electrons enter a system, such as an electrolytic cell or an electron tube. The first cathode ray tube scanning device was invented by the German scientist Karl Ferdinand Braun in 1897. Braun introduced a CRT with a fluorescent screen, known as the cathode ray oscilloscope. The screen would emit a visible light when struck by a beam of electrons. -
Plum Pudding Model
With this model, Thomson abandoned his earlier "nebular atom" hypothesis in which the atom was composed of immaterial vortices. Now, at least part of the atom was to be composed of Thomson's particulate negative corpuscles, although the rest of the positively charged part of the atom remained somewhat nebulous and ill-defined. -
Gold Foil Experiment
Ernest Rutherford, a New Zealander, designed an experiment to study how alpha particles. Rutherford bombarded a very thin piece of gold foil with a stream of positively charged particles known as the alpha particles. he found that most of the alpha particles passed straight through the foil. This shows that most of the atom is empty space. -
Robert Millikan
Millikan began a series of experiments in 1909 that studied electrical charges, more specifically, electrical charges carried by electrons. His discovery was accomplished by spraying minute drops of oil into a specially built chamber. It is known as the Millikan oil-drop experiment. -
Ernest Rutherford
Ernest Rutherford performed an experiment where he shot alpha particles at gold foil, expecting them to pass right through. Some bounced back, however, and he formulated the planetary model, which showed that most of the mass of an atom was concentrated in the center (nucleus). -
Rutherford Model
Rutherford tested Thomson's hypothesis by devising his "gold foil" experiment. Rutherford reasoned that if Thomson's model was correct then the mass of the atom was spread out throughout the atom. Then, if he shot high velocity alpha particles (helium nuclei) at an atom then there would be very little to deflect the alpha particles. He decided to test this with a thin film of gold atoms. As expected, most alpha particles went right through the gold foil but to his amazement a few alpha particles -
Henry Moseley
Henry Moseley studied under Rutherford and brilliantly developed the application of X-ray spectra to study atomic structure; Moseley's discoveries resulted in a more accurate positioning of elements in the Periodic Table by closer determination of atomic numbers. Tragically for the development of science -
Bohr Planetary Model
In the Bohr Model the neutrons and protons (symbolized by red and blue balls in the adjacent image) occupy a dense central region called the nucleus, and the electrons orbit the nucleus. -
Neils Bohr
Niels Bohr applies quantum theory to Rutherford's atomic structure by assuming that electrons travel in stationary orbits defined by their angular momentum. This led to the calculation of possible energy levels for these orbits and the postulation that the emission of light occurs when an electron moves into a lower energy orbit. -
Erwin Schrodinger
Edwin Schrodinger stated that rather than electrons being distributed within an electron configuration of shells and energy levels, they were arranged in orbitals which were systematically distributed within Electron Clouds. He defined an orbital as: The region of space that surrounds a nucleus in which two electrons may randomly move. -
Electron Cloud Model
The cloud model represents a sort of history of where the electron has probably been and where it is likely to be going. The red dot in the middle represents the nucleus while the red dot around the outside represents an instance of the electron. Imagine, as the electron moves it leaves a trace of where it was. This collection of traces quickly begins to resemble a cloud. -
Quantum mechanical model
The quantum mechanical model is based on quantum theory, which says matter also has properties associated with waves. According to quantum theory, it’s impossible to know the exact position and momentum of an electron at the same time. The quantum mechanical model of the atom uses complex shapes of orbitals, volumes of space in which there is likely to be an electron. So, this model is based on probability rather than certainty. -
James chadwick
Chadwick in collaboration with Rutheford realized that the atomic mass of most elements was about double the number of protons. For example, helium has an atomic mass of about 4 and only 2 protons. Electrons have minimal relative mass, so they postulated that a neutral particle may exist. In 1932, he found definitive evidence for the existence of a neutral particle that had roughly the same mass as a proton. He discovered the neutron.
