THE STRUCTURE OF ATOM (Ch 6)

The structure of an atom is the basic unit of matter consisting of a nucleus and its negatively charged electron cloud surrounding it. The nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in Hydrogen-1 which has no neutrons). The electrons in an atom bound to the nucleus by the electromagnetic force. Similarly, a collection of atoms can bind to each other to form a molecule. Atoms containing the number of protons and electrons of the same neutral, while containing the number of protons and electrons of different positive or negative and is ion. Atoms are grouped based on the number of protons and neutrons in the atomic nucleus. The number of protons in an atom determines the chemical element the atom, and the number of neutrons determine the isotope of the element. 
PARTICLE MATERIALThe smallest part of matter called particles.Some opinions about particles of matter:1. According to Democritus, the distribution of matter is discontinuous (if the material is divided and continues to be divided then finally obtained the smallest particle that could no longer be divided = called Atom)2. According to Plato and Aristotle, the distribution of matter is continuous (division can continue indefinitely)Basic Postulates of Dalton Atomic Theory:1) All matter is composed of minute particles called atoms2) The element is composed of material similar atoms3) Atoms of an element are identical but different from atoms of other elements (having different masses)4) The compound is a material consisting of two or more types of atoms with a certain ratio5) Atoms can not be created or destroyed and can not be converted to other atoms through chemical reactions normal. The chemical reaction is the rearrangement (reorganization) of the atoms involved in the reaction
 The downside of Dalton Atomic theory postulates:1) Atom is not something that is not divided, but rather made up of subatomic particles2) Atoms of the same element may have different masses (called isotopes)3) Atoms of an element can be changed into atoms of other elements through nuclear reactions4) Some of the elements are not made up of atoms instead of molecules 
ATOMIC THEORY DEVELOPMENT1). Atomic Model Daltona) Atom described as a very small solid ball.b) Atoms are the smallest particles that can not be broken again.c) Atoms of an element have the same same, while the atoms of different elements, different in mass and nature.d) Compounds are formed when atoms combine with each other.e) A chemical reaction is the reorganization of atoms, so there is no atom has changed due to chemical reactions.
 Dalton's atomic theory is supported by the second law of nature, namely:1. Law of Conservation of Mass (Lavoisier law): the mass of substances before and after the reaction is the same.2. Keep Comparative Law (law Proust): comparison of mass elements that make up a substance is fixed.Weakness Atomic Model Dalton:1) Can not explain the difference between a single atom elements with other elements2) Can not explain the electrical properties of materials3) Can not explain how atoms bond together4) According to Dalton's atomic theory of number 5, no atom has changed due to chemical reactions. Now it turns out the reactions of nuclear chemistry, an atom can change into other atoms.2). Thomson Atomic ModelAfter the discovery of the electron by JJ Thomson, Thomson atomic model formulated which is a refinement of the atomic model of Dalton. According to Thomson:a) Atoms consist of a positively charged material and in which the electrons are scattered (like raisins in raisin bread)b) Atoms are neutral, the positive charge and negative charge the same amount
 3). Rutherford Atom Modela) Rutherford found evidence that the atomic nuclei are positively charged, are smaller than the size of the atomic mass of an atom but almost entirely from the point masses.b) Atoms consist of a positively charged nucleus and are at the center of the atom and the electrons move through the nucleus (like planets in the solar system).c) Atoms are neutral.d) The radius of the nucleus and atomic radii can be determined.Weakness Rutherford Atomic Model:Ø Inability to explain why the electrons do not fall into the nucleus due to electrostatic attractive forces the core to the electron.Ø According to Maxwell's theory, if the electrons as charged particles around the core that has the opposite charge then the trajectory will spiral and will lose power / energy in the form of radiation and eventually fell to the core.4). Niels Bohr Atom Model• atomic model based on quantum theory to explain the spectrum of hydrogen gas.• According to Bohr, the line spectrum indicates that the electrons only occupy certain energy levels in the atoms.He said:a) Atoms consist of a positively charged nucleus and the surrounding circulating electrons are negatively charged.b) Electrons orbit around the nucleus of an atom in a particular orbit known as the stationary state of motion (fixed), hereinafter referred to as the main energy level (electron shell), which is expressed by the principal quantum number (n).c) During the electrons are in a stationary orbit, its energy will remain so no light is emitted.d) The electrons can only move from the lower stationary trajectory to a higher stationary trajectory if absorbing energy. Conversely, if the electrons move from a higher stationary trajectory to lower the release of energy.e) In the normal state (without outside influence), the electrons occupy the lowest energy level (called the basic level = ground state)Niels Bohr Atom Model Weaknesses:1. Just to explain the spectrum of the atom or ion containing one electron and is not in accordance with the spectrum of electron atoms or ions that much.2. Not being able to explain that atoms can form molecules through chemical bonds5). Modern Atomic ModelDeveloped based on the theory of quantum mechanics is called wave mechanics; initiated by 3 experts:a) Louis Victor de BroglieStating that the material has the properties of a material dualism, and as waves.b) Werner HeisenbergPut forward the principle of uncertainty for the material is of a particle and a wave. Distance or location of electrons that surround the nucleus can only be determined by the possibility - probability alone.c) Erwin Schrodinger (refining models Bohr Atom)Successfully prepared for electron wave equation using the principle of wave mechanics. Electrons surrounding the nucleus contained in an area that is 3-dimensional orbital around the nucleus where electrons with a specific energy can be found with the greatest possible.Modern atomic models:a) Atoms consist of a nucleus containing protons and neutrons while the electrons moving around the nucleus and are at particular orbitals of atoms that make up the skin.b) the area of ​​the 3-dimensional orbital around the nucleus where electrons with a specific energy can be found with the greatest possible.c) The position of electrons in the orbital-orbital quantum numbers stated.• Orbital described as a cloud of electrons, namely: the forms of space where an electron is likely to be found.• The meeting of the electron cloud, the more likely the electron was discovered and vice versa.