teori-teori atom

The name "atom" comes from the Greek is "atomos" introduced by Democritus (4-5 BC) which means it can not be subdivided or any part of the smallest of matter that can not be subdivided.
1. John Dalton's Atomic Theory In 1803, John Dalton put forward put forward pendapatnaya about atoms. Dalton's atomic theory was based on two laws, namely the law of conservation of mass (Lavoisier law) and legal permanent arrangement (legal prouts). Lavosier mennyatakan that "The total mass of substances before the reaction will always equal the total mass of the reaction substances". While Prouts states that "Comparison of the mass of the elements in a compound always remain". From both legal Dalton expressed the opinion of the atoms as follows: 1. Atoms are the smallest part of matter that has not be subdivided 2. Atom is described as a very small solid ball, an element has atoms are identical and different for different elements 3. Atoms combine to form compounds with a ratio of integers and simple. For example, water consists of hydrogen atoms and oxygen atoms 4. The chemical reaction is the separation or amalgamation or a rearrangement of atoms, so that atoms can not be created or destroyed. Weakness of Dalton's theory is not to explain the relationship between the solution and the compound electric current conductivity.
2. J. Atomic Theory J. Thomson Based on the discovery of a better cathode tube by William Crookers, then JJ Thomson further research on cathode rays and can be ascertained that cathode rays are particles, because it can rotate a propeller that is placed between the cathode and anode. From the results of this experiment, Thomson stated that cathode rays are particles making up the atom (subatomic particles) are negatively charged and hereinafter referred to as electrons. Atoms are neutral particles, because electrons are negatively charged, then there must be another particle-laden positifuntuk menetrallkan negative charge of the electron. From its discovery, the Thomson fix weaknesses of daltons atomic theory and atomic theory proposed, known as Thomson's Atomic Theory. Which states that: "Atom is a solid ball is positively charged and negatively charged electrons scattered didalamya" Atomini model can be described as guava already exfoliated skin. cashew marata describe electrons scattered in a solid pink meat balls, which is analogous to the Thomson atomic model as a solid ball positive. Thomson atomic model can be described as follows: Weakness that atoms models developed by Thomson, that is not able to explain the arrangement of positive and negative charges in the atomic sphere.
3. Rutherford Atomic Theory Rutherford with two of his disciples (Hans Geigerdan Erners Masreden) conducted an experiment known as the scattering of alpha rays (λ) of thin plates of gold (pure metal at the time). Previously have found the alpha particles, ie particles are positively charged and move straight, powerful large translucent so that it can penetrate a thin sheet of paper. The experiment was actually intended to test Thomson's opinion, namely whether the atom is really a ball of solid positive when subjected to alpha particle will be reflected or deflected. From their observations, obtained the fact that an alpha particle is fired at a very thin gold plate, then most of the alpha particles passed (there is a deviation angle of less than 1 °), but from the observations obtained Marsden fact that one in 20,000 alpha particles will turn an angle of 90 · Even more. Based on the symptoms that occur, some obtained some kesipulan following: 1. Atom is not a solid ball, because almost all the alpha particles passed 2. If the gold plate is regarded as one lapisanatom-atom gold, then gold atoms in very small particles are positively charged. 3. Such particles are partikelyang construct a nucleus, based on the fact that 1 in 20,000 alpha particles will be deflected. When the ratio of 1:20,000 is a comparison of the diameter, the size of the nuclei obtained about 10,000 smaller than the overall size of the atom. Based on facts obtained from these experiments, Rutherford proposed a model of the atom, known as Rutherford Atomic Model which states that the Atomic nuclei are composed of very small and positively charged, surrounded by negatively charged electrons. Rutherford assumed that nuclei contained within the neutral particles that function binding the positive particles repel each other not to. Weaknesses of the theory described by Rutherford, namely: Can not explain why electrons do not fall into the nucleus of an atom.
4. Bohr Atomic Theory There 1913, Danish physicist Neils Bohr called failures to improve through the experiments of Rutherford's atomic spectrum of hydrogen atoms. These experiments successfully deliver state of the electrons in the picture occupies the area around the atomic nucleus. Bohr's explanation involves a combination of hydrogen atoms between the classical theory of Rutherford and from Planck's quantum theory, expressed by the four postulates, as follows: 1. There are only a certain set of orbits allowed for single electron in a hydrogen atom. This orbit is known as a stationary state of motion (settled) electrons and is a circular path around the core. 2. As long as the electrons are in a stationary trajectory, the electron energy remains so there is no energy in the form of radiation emitted or absorbed. 3. Electrons can only move from one stationary trajectory into another stationary trajectory. In this transition, a certain amount of energy involved, the magnitude according to the Planck equation, ΔE = hv. 4. Stationary trajectory is allowed to have the scale with specific properties, particularly a property called angular momentum. The amount of angular momentum is a multiple of h/2Π or nh/2Π, where n is an integer and h Planck constant. According to Bohr's atomic model, the electrons surrounding the nucleus in certain paths called electron shells or energy levels. Lowest energy level is the electron shell which is located in, getting out of her skin and the greater the number the higher the energy level. Weaknesses: This atomic model of explanation can not explain the spectrum of color from many electron atoms.
5. Modern Atomic Theory Atom model of quantum mechanics developed by Erwin Schrodinger (1926). Before the Erwin Schrodinger, an expert from the German Werner Heisenberg developed the theory of quantum mechanics known as the uncertainty principle is "not possible to determined the position and momentum of an object closely at the same time, which can determined is the probability of finding the electron at a certain distance from the nucleus ". Region of space around the core with the probability to gain electrons called orbitals. The shape and the orbital energy levels were formulated by Erwin Schrodinger Schrodinger.Erwin solve an equation to obtain the wave function to describe the discovery of a possible limit of electrons in three dimensions. Model of the atom with the orbital trajectory of the electron is called a model of modern atomic or atomic model of quantum mechanics that applies to this Characteristic of wave mechanics model of the atom 1. The movement of electrons have wave properties, so that the trajectory (orbit) is not stationary like the Bohr model, but following the completion of the square is called the orbital wave function (three-dimensional shapes darikebolehjadian greatest discovery of the electron with a particular state in an atom) 2. The shape and size of the orbitals depends on the price of the three numbers kuantumnya. (Electrons that occupy the orbital quantum number is expressed as) 3. The position as far as 0.529 electron from the nucleus H Armstrong by Bohr instead of something definite, but it is the biggest opportunity bolehjadi discovery of electrons.