Atoms

September 21 2009ATOM AND ATOMIC STRUCTURE.
 17 Votes


    A. INTRODUCTIONDnature of this module you will learn some of the atomic theory and the development of the periodic system of elements. As we know that all things in nature is certainly made up of particles called atoms minuscule. In the development of the atom apparently is not the smallest particles as forming an object or a compound, but the atom is made of elementary particles are smaller. In this module you will also be able to compare some expert opinion about the structure of the atom.Of the many elements there are, of course people will have difficulty when studying the properties of these elements. To make it easy, some experts classify these elements. First performed in simple grouping is based on the nature kelogaman, the next grouping of increasing atomic mass. Grouping turns out there are a lot of weaknesses, eventually grouping elements is based on the atomic number increases. This grouping is a big improvement, because it can be linked to the chemical properties, physical properties, and mass elements are still there are few drawbacks though.ATOM MODEL DEVELOPMENT

    1. Atomic Model DaltonThe period since the beginning of modern chemistry proposals of John Dalton's atomic theory in his book "New system of chemical philosophy" 1808. Long before Dalton actually several theories have been put forward by the Greek scientist Democritos Leucippos, followed by the third century BC. However, Dalton's theories are highly complementary and more appropriate, so the theory is able to develop chemistry.In 1808, a chemist John Dalton of the English suggested the idea of ​​atoms as the constituent particles of matter. According to Dalton's atomic theory:

    Atoms are the smallest particles that can not be subdivided.
    Atoms of the same element have the same weight, while the atoms of different elements will be different, which means it has a different weight.
    The compound is said to be the result of the merging of atoms are not the same as the ratio of the weight that is proportional to the weight of atoms joined it.
    Chemical reactions involve only penataulangan atoms so that no atom has changed due to chemical reactions.

 The word atom is actually derived from the Latin atomos, which means no terbelahkan.

    2. Thomson Atomic ModelThe discovery of electrons on the merit J. J Thomson and R. Millikan in the first years of the 20th century provide evidence of imperfection Dalton atomic model. JJ Thomson detailing Dalton atomic model that suggests, that in the atom the electrons are spread evenly in the "ball" positively charged. The situation is similar to raisin bread. Raisins (depicted as electrons) are scattered in all parts of the bread (compared to a positively charged sphere).

    3. Rutherford Atomic Model and LoopholesRutherford proposed the theory of atoms, namely:

    Most of the atoms in the form of empty space, so all atomic mass centered on the nucleus of an atom is very small.
    Atom is composed of:

    The nucleus is positively charged.
    Electrons are negatively charged atom surrounding the nucleus.

    The entire central proton in the nucleus.
    The number of protons in the nucleus equals the number of electrons surrounding the nucleus, so the atom is neutral.From the theory, Rutherford's atom model in the solar system, the electrons moving around the nucleus like planets around the sun. For example, a hydrogen atom has a nucleus charged +1, then the charge is offset by one electron orbiting the nucleus.One objection of postulates Rutherford is for electrons moving in an orbit, then there is acceleration towards the center, these electrons emit radiation continuously and gradually releases energy that will eventually fall into the nucleus.This is not possible because it is a stable atom anyway this model is not able to obtain data from the research spectrum of atomic elements.

    4. Bohr Atom ModelIn 1913, Niels Bohr proposed a model that can be explained by atomic hydrogen spectra. He accepted this concept as proposed by Rutherford, but by applying the quantum theory of radiation as developed by Planck and Einstein to explain the properties of electron planet system.
Bohr postulate reads:

    Electrons in an atom to orbit around the nucleus in specific orbits. Each orbit has a specific energy and energy level of an electron is fixed at while in orbit. Electrons that are at this level is called stationary levels and each level of energy called energy levels or the skin. Electron energy levels are not radiate energy.
    Emission and absorption of energy in the form of radiation can only be generated when an electron moving from the stationary to the other levels.
    No energy is emitted or absorbed slowly, but in units / hu package (called a quantum), where h is Planck's constant and u is the frequency of the radiated energy.
    Furthermore the energy levels of the nucleus, the more energy too. Energy is absorbed when an electron jumps from orbit to orbit the inside of the outer. Energy will be emitted when an electron moves from an outer orbit to orbit deeper. The amount emitted quantum or diabsorpsikan can be determined from the electron energy levels of the early and the final level after reaching a stationary state. When E2 and E1 are each beginning and ending energy levels, being? frequency is then:
    å E = E1 - E2 = h.u
    Energy in each orbit is affected by the conditions in which the angular momentum (nut) electrons moving in its orbit has a certain value which is simply a multiple of h/2u . With m = mass of the electron, u = velocity, r = radius of orbit, h = Planck's constant, and n = orbit occupied by electrons (1, 2, 3, ...... or as letters K, L, M, ....... ).
    5. Wave Mechanics Atomic ModelIn 1924, Louis de Broglie French physicist Nobel Prize winner in 1929, concluded that the electrons in an atom can be regarded as a particle and a wave. As a result of dualistic nature of electrons, Heisenberg Nobel prize winner for physics in 1926 put forward the principle of uncertainty, which is not possible to know simultaneously the position and velocity of the electron.For this reason Bohr pictured the electron trajectory is impossible. That can be said is the probability of an electron in an atom have found in certain spaces in the so-called atomic orbitals. The idea that electrons are in orbitals around the nucleus of an atom is the latest model of the atom.In 1926, a physicist Erwin Schrodinger Austrian Nobel Prize winner for physics in 1933, managed to formulate the wave equation to describe the motion of electrons in atoms. Energy and geometrical orbitals as we have learned, are derived based on calculations using the Schrodinger wave equation.




SUMMARYv According to Dalton's atomic theory:

    Atoms are the smallest particles that can not be subdivided.
    Atoms of the same element have the same weight, while the atoms of different elements will be different, which means it has a different weight.
    The compound is said to be the result of the merging of atoms are not the same as the ratio of the weight that is proportional to the weight of atoms joined it.
    Chemical reactions involve only penataulangan atoms so that no atom has changed due to chemical reactions.v According to J. J. Thomson: That in the atom the electrons are spread evenly in the "ball" positively charged. The situation is similar to raisin bread.v Rutherford atomic theory:

    Atom is composed of:

    The nucleus is positively charged.
    Electrons are negatively charged atom surrounding the nucleus.

    In a neutral atom, the number of positively charged atomic nucleus equal to the number of electrons.v Bohr Postulates of atoms:

    Electrons in an atom to orbit around the nucleus in an orbit / certain energy level.
    Furthermore the energy levels of the nucleus, the more energy too.
    Energy will be emitted when electrons move from a high energy level to a lower energy level.
    Energy will be absorbed when an electron moves from a low energy level to a higher energy level.
    No energy is emitted or absorbed slowly, but in units / h package? (Called a quantum).v Model Atomic Wave Mechanics

    That the electrons in the atom as a particle and a wave.
    Heisenberg uncertainty principle put forward, which is not possible to know simultaneously the position and velocity of the electron.
    c. So the probability of an electron in an atom have found in certain spaces in the so-called atomic orbitals.

MOLECULE
The molecule is defined as a group of atoms (at least two) are linked to each other by very strong (covalent) in a particular order and is electrically neutral, and is quite stable. [1] [2] According to this definition, in contrast to ions polyatomic molecules. In organic chemistry and biochemistry, the term molecule is used less rigid, so that the charged organic molecules and biomolecules including molecules were considered.

In the kinetic theory of gases, the term molecule is often used to refer to any gas particles without depending on its composition. [3] According to this definition noble gas atoms are considered molecules despite the gases consist of a single atom that is not bonded. [4 ]

A molecule may consist of atoms that element of the same (eg O2 oxygen), or made ​​up of different elements (eg water H2O). Atoms and complexes connected by non-covalent (eg bound by hydrogen bonds and ionic bonds) are generally not considered as a single molecule. Molecular and chemical formula:  

a. Molecular Elements
Oxygen is formed from two atoms of the same, namely oxygen. The chemical formula of oxygen is O2. Molecules are made ​​up of one type of atom is called an element molecules. Examples of other elements are molecules Cl2, I2, Br2, and P4.

b. Molecular Compounds
Molecules are composed of more than one kind of atom is called molecular compounds. Examples of molecular compounds, ie water which has the chemical formula H2O. Water is composed of two H atoms and one O atom

Molecular compounds and their chemical formula
 
Molecular compounds and their chemical formula
Molecular elements and molecular compounds can be distinguished by the number of types of constituent atoms. These differences can you see on the molecular elements of H2 and H2O molecules compounds.

In everyday life, we constantly interact with the molecules of elements and molecular compounds. For example, when breathing, we inhale oxygen constituent molecules (O2) and molecular compounds release carbon dioxide (CO2) and water (H2O) in the form of water vapor.

ION
At the beginning of the 19th century, Dalton reveals that the smallest particles of matter are atoms. In the mid-19th century, a lot of research showing that many substances are not composed by atoms but by charged particles called ions. The particle size is about the size of atoms and molecules. Example: people already know that the molten salt and the salt solution in water can conduct electricity. In the event, an electrical charge to flow in a different way than in the metal. In metals, the electrical charge carried by electrons. Conversely, in a molten salt or a salt solution in water, the electrical charge carried by the ions (positive and negative ions).
Thus, the smallest particles of matter not only in the form of atoms and molecules, but can also form ion. Electron charge is the smallest amount of charge is called the elementary charge (e). Ion charge is a one-time or multiple times the elementary charge. Therefore, the ion charge number is only written with one or multiple of the charge. Metals form positively charged ions (cations). Ions most nonmetallic elements form a negatively charged ion (anion).
The atoms in neutral containing positive and negative charges of the same amount. Atoms turn into ions when receiving or releasing electrons (see the picture). Is an ion-charged one or more times of the elementary charge can be estimated from the location of the corresponding elements in the periodic system of elements? Alkali metal ions (IA) always form positively charged ions one, such as lithium ion (Li +), sodium ions (Na +) and potassium ions (K +). Ions of alkaline earth metals (IIA) has two positive charges, such as calcium ions (Ca2 +) and magnesium (Mg 2 +).
As with ions of metals, ions of nonmetal elements can be estimated based on the location of the load these elements in the periodic system of elements. The ions of the halogen group elements (VIIa) is always negatively charged one, namely fuorida ion (F-), chloride ions (Cl-), bromide ion (Br-), and iodide ions (I-). The ions of the VIA group, such as oxygen to form two negatively charged ions, oxide (O2-) or sulfur which also form two negatively charged ions, sulfda (S2-). Of elements of group VA, people familiar with the elements nitrogen capable of forming three negatively charged ions, nitride (N3-). The elements of group VIIIA noble gases do not form ions ion.Di aside from a single element atoms (monatomic), there are also ions derived from the combined
two or more atoms of different elements (polyatomic). For example, sulfate ions negatively charged two (SO42-), ion nitrate negatively charged one (NO3-), acetate ions negatively charged one (CH3COO-), ammonium ions are positively charged one (NH +) and hydroxyl ions are negatively charged one ( OH-).
Substances that are composed of ions have a neutral electrical charge. It is caused by a number of positive and negative charges are equal. Example: sodium chloride (NaCl) is composed of a positively charged sodium ion and a negatively charged chlorine ions in the ratio 1: 1, magnesium chloride (MgCl2) is composed of a positively charged magnesium ions two and two negatively charged chlorine ions in the comparison of the amount of magnesium ions and the amount of chlorine ions is 1: 2. Thus, the amount of positive charge from the magnesium ions equal to the amount of negative charge from the chlorine ions. In aluminum chloride (AlCl3), a positively charged aluminum ion three neutralized by three negatively charged chlorine ion one. Between positive ions and negative construct a salt mutual attraction to one another to form a crystal lattice. Crystal lattice is various types, depending on the range of proportions of positive and negative ions that bind. Here is described a model of the crystal lattice of the compound salt or sodium chloride (NaCl).
NaCl crystal lattice model
In the picture above shows that the sodium ion is surrounded by six chlorine ions. Conversely, a chlorine ion is surrounded by six sodium ions. Regularity is owned by each ion of sodium and chlorine ions. Thus, the two reactions do not form molecules but form a crystal lattice. Each ion remains in place. This could explain why the solid salt can not conduct electricity, while the discharge can conduct electric current. When sodium chloride (NaCl) is dissolved in water the NaCl crystal lattice will decompose to form sodium ions and ionklor.
Both of these ions will interact with water molecules, as shown in the picture. Charged ions have opposite electrical attraction force is strong. Chemical bonding that occurs because the force of electric attraction is called an ionic bond. Compounds are formed due to ionic bonds are called ionic compounds. The existence of strong gravity could explain why the salts or ionic compounds generally have high melting and boiling points are high, much higher than substances composed of molecules.
An atom is said to be neutral if the number of protons equals the number of electrons.If a neutral atom captures an electron, the number of electrons will be more than the number of protons. The atom is said to capture electrons are negatively charged atoms.If a neutral atom loses electrons, then the number of protons will be more than the number of electrons. The atom loses electrons is said to be positively charged.Electrically charged atoms called ions. Positive ions are called cations and negative ions are called anions.Ions are atoms or groups of atoms that accept or release electrons.Salt (NaCl) is an example of merging with the Na + cation-anion Cl.