STRUCTURE ATOM ( CH 6 )

PARTICLE MATERIAL

The 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 atoms
2) The element is composed of material similar atoms
3) 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 ratio
5) 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 particles
2) 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 reactions
4) Some of the elements are not made ​​up of atoms instead of molecules

ATOMIC THEORY DEVELOPMENT
1). Atomic Model Dalton
a) 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 elements
2) Can not explain the electrical properties of materials
3) Can not explain how atoms bond together
4) 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 Model
After 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 Model
a) 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 bonds

5). Modern Atomic Model
Developed based on theories of quantum mechanics called wave mechanics; initiated by 3 experts:
a) Louis Victor de Broglie
Stating that the material has the properties of a material dualism, and as waves.
b) Werner Heisenberg
Put 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.

ENERGY AND CHEMICAL REACTION"ENTHALPY" (CH 5)

Enthalpy changeA.PERUBAHAN enthalpy STANDARD (ΔH0)Measurement standard state enthalpy change is at a temperature of 298 K and pressure of 1 atm. The state standard is needed because measurements at different temperatures and pressures will result in different prices enthalpy change pula.Beberapa types of standard enthalpy change, the change in the standard enthalpy of formation (ΔHfo), the standard enthalpy change of decomposition (ΔHdo), and the change in enthalpy standard combustion (ΔHco).a.Perubahan entali establishment of standards (ΔHfo)Standard enthalpy change of formation (standard enthalpy of formation) is the enthalpy change that occurs in the formation of 1 mole of a compound from its elements are most stable at the standard state.Unit peruvbahan standard enthalpy of formation according to the international system (SI) is kilojoul per mole (kJ mol-1).b.Perubahan standard enthalpy of decomposition (ΔHdo)Standard decomposition enthalpy change (standard enthalpy of de composition) refers enthalpy changes that occur in the decomposition of 1 mole of a compound into its elements are most stable at the standard state.Basically, the standard enthalpy change of decomposition as opposed to the standard enthalpy change of formation, then the price would be berlawanya.c.Perubahan standard enthalpy of combustion (ΔHco)Standard combustion enthalpy change (standard entalpy of combustion) is the enthalpy change that occurs in the burning of one mole of a substance completely.Combustion is a reaction of a substance, including the following:1.C (S) + O2 (g) → CO2 (g)2. H2 (g) + ⅟ 2 O2 (g) → H2O (g)3.S (S) + O2 (g) → SO2 (g)B.PENENTUAN enthalpy change1.KALORIMETRIThe enthalpy change is the heat change is measured at constant teknan. Therefore, to determine the enthalpy changes take place in the same way denagn determination done peerubahan heat at constant pressure.The change is a transfer of energy that occurs as a result of perbedaab suhu.jadi, heat pad changes a reaction can be measured by measuring the temperature changes that occur.Measurement of heat changes can be done using a tool called the calorimeterBomb calorimeter (bomb calorimeter) is a specifically designed calorimeter, sehinngga system is really in a state of isolation.Picture: Bomb Calorimeter.In the bomb calorimeter there is a special room called the bomb, crazy filled with oxygen gas at high pressure. Bomb calorimeter in a bertisi immersed in water used to hold the sample combustion reaction.The system in the bomb calorimeter is everything that is in the bomb calorimeter, covering: the reqaksi (bombs), water thermometer, stirrer and others.Combustion reactions that occur in the bomb, it will generate heat and absorbed by the water and the bomb at the same temperature, which are shown by the increase in water temperature. Therefore considered that there is no heat absorbed by the system and in the release into the environment during the reaction, thenqreaksi qbom + q + water = qsisteraor qreaksi qbom + water + q = 0qreaksi = - (q + qbom water)The amount of heat absorbed by the bomb can be calculated by measuring the heat capacity of the bomb.With, Cbom = heat capacity of the bomb (J0C-1 or JK-1)ΔT = change in temperature (° C or K)The amount of heat that causes the temperature change (increase or decrease in temperature) water contained in the calorimeter formulated as:By: m = mass of water in the calorimeter (g)c = specific heat in the calorimeter (J g-1K-1)ΔT = change in temperature (K or ° C)Calorimeter who either have a small heat capacity. That is, the calorimeter is really as an isolated system, so that changes, the heat of reaction in the bombing occurred only affect changes in water temperature or solution in the calorimeter.The reaction takes place in a bomb calorimeter is a reaction that takes place at a constant volume (ΔV = 0), the heat changes that occur in the system will be equal to the change nergi it.ΔU = q + w, where w =-p ΔVPengikuran heat of reaction than the reaction heat of combustion, can be done using a calorimeter at constant pressure. For example, the styrofoam calorimeter which is made from styrofoam cups. Calorimeter of this type generally done to measure the heat of reaction in which the reaction takes place in solution, for example, to measure the heat changes that occur in acid-base neutralization reactions.In a chemical reaction calorimeter takes place at constant pressure (Δp = 0), the heat changes that occur in the system will be equal to the enthalpy change.ΔH = qpIt is therefore considered that there is no heat absorbed by the system and in the release into the environment during the reaction, thenqreaksi + q = q calorimeter systemor qreaksi + q calorimeter = 0qreaksi = - (q + calorimeter qlarutan)If the price of the calorimeter heat capacity is very small, it can be ignored, so that the heat can be considered only changes result in an increase in the calorimeter sahu solution.a, m = mass of the solution in the calorimeter (g)c = specific heat of solution in the calorimeter (J g-1 K-1 or J g-1C-1)ΔT = change in temperature (K or 0C)

C.HUKUM HESS
 a  chemist named GHHess Russian citizens in 1840 researching the truth that is free of chemical reactions on a journey through several stages of heat will affect the reaction.
Hess's Law is a law in physical chemistry for the expansion of Hess in Hess cycle. This law is used to predict the enthalpy change of the law of conservation of energy (expressed as a state function ΔH).
According to Hess's law, because enthalpy is a state function, the enthalpy change of a chemical reaction is the same, although the measures used to obtain different products. In other words, only the initial state and the final effect on the change in enthalpy, not the steps taken to achieve it.
This causes a change in enthalpy of a reaction can be calculated even can not be measured directly. The trick is to perform arithmetic operations on an equation known enthalpy changes. Equations are arranged so that the sum of all the equations will produce the reaction we want. If an equation is multiplied (or divided) by a number, the enthalpy changes must also be multiplied (divided). If the equation is reversed, then the sign of the enthalpy changes must be reversed as well (ie be-ΔH).
In addition, by using the law of Hess, ΔH value can also be determined by the reduction of the enthalpy of formation of the products minus the enthalpy of formation of the reactants. mathematically

For other reactions in general
  
 Hess's Law states that the overall enthalpy change of a process depends only on the initial state and the end of the reaction, and does not depend on the route or the steps in between. By knowing ΔHf (change in enthalpy of formation) of the reactants and products, it can be predicted enthalpy change of any reaction, according to the formula

 ΔHfP-ΔH ΔH = fR

Enthalpy change for a reaction can also be predicted from the change in enthalpy combustion reactants and products, with the formula

         ΔH =-ΔHcP + ΔHcR
The concept of Hess's law can also be extended to calculate the change in the function of other circumstances, such as entropy and free energy. Both of these applications is useful because magnitudes are difficult or can not be measured directly, so the calculations with Hess's law is used as a way to determine

Stoichiometric ( CH 4 )

Stoichiometric


Stoichiometry derived from the Greek, from the word meaning stoicheion element and metron meaning measure. Stoichiometric mass relationships antarunsur discussed in a compound (stoichiometric compounds) and antarzat in a reaction (reaction stoichiometry). The measurement of mass in a chemical reaction initiated by Antoine Laurent Lavoisier (1743 - 1794) who found that the chemical reaction does not change the mass (the law of conservation of mass). Furthermore, Joseph Louis Proust (1754 - 1826) discovered that the elements form a compound in a certain ratio (comparative law anyway). Furthermore, in order to construct atomic theory, John Dalton discovered the basic laws of chemistry the third, called the law of multiple comparisons. The third law is the basis of the theory of the first chemical, the atomic theory proposed by John Dalton around 1803. According to Dalton, all matter is composed of atoms, elements consist of a type of atom, whereas compounds composed of different atoms in a certain ratio. However, Dalton has not been able to determine the ratio of atoms - atoms in the compound (chemical formula of the substance). Determination of the chemical formulas of substances can be done thanks to the discovery of Gay Lussac and Avogadro. After the chemical formula of compounds can be determined, then the mass ratio antaratom (Ar) and intermolecular (Mr) can be determined. Knowledge of the relative atomic mass and chemical formula of the compound is a basic chemical calculations.


a. The initial phase of stoichiometric


At the beginning of chemistry, quantitative aspects of chemical change, the chemical reaction stoichiometry, did not get much attention. Even when attention has been given, experimental techniques and tools do not produce correct results.


One example involves the theory of phlogiston. Flogistonis tried to explain the phenomenon of combustion with the term "flammable substance". According to the flogitonis, arson is a release of a substance can be etrbakar (from the burning substance). This substance was later called "phlogiston". Based on this theory, they defined as the release of phlogiston combustion of flammable substances. Mass changes when burning wood fits well with this theory. However, the change in mass of metal when calcined does not match the theory. However flogistonis accept that the two processes are essentially identical. Increasing the mass of calcined metal is a fact. Flogistonis tried to explain this anomaly by stating that phlogiston negative mass.


Philosophers of Flanders January Baptista van Helmont (1579-1644) experimented "willow" famous. He is growing seedlings of willow after measuring the mass of flower pots and soil. Since there is no mass change flower pots and soil when the seed grows, it assumes that the masses were obtained only because of water coming into the ore. He concludes that "the root of all matter is water". Based on the current outlook, hypothesis and experiment are far from perfect, but the theory is a good example of the attitude of the quantitative aspects of chemistry that are growing. Helmont recognize the importance of stoichiometry, and clearly ahead of his time.


In the late 18th century, German chemist Jeremias Benjamin Richter (1762-1807) invented the concept of equivalent (in terms of modern chemistry chemical equivalent) with a reaction carefully acid / base, the quantitative relationship between acids and bases in the neutralization reaction. Equivalent Richter, or what is now called the chemical equivalent, indicating a certain amount of material in the reaction. The neutralization equivalent in regard to the relationship between the number of acid and a base for mentralkannya. Proper knowledge is essential to produce the equivalent of soap and gunpowder good. Thus, such knowledge is very important in practice.


At the same time Lavoisier established the law of conservation of mass, and provide a basis equivalent to the concept of an accurate and creative experiments. Thus, the stoichiometry handle the quantitative aspects of chemical reactions into chemical basic methodology. All the fundamental laws of chemistry, of the law of conservation of mass, the law of comparative law remains until all based gas reaction stoichiometry. Fundamental laws are the basis of the atomic theory, and consistently explained by atomic theory. However, it is interesting to note that the concept of equivalent used before atomic theory was introduced.


b. The relative atomic mass and atomic mass


Dalton recognized that it is important to determine the mass of each atom as mass varies for each type of atom. Atom is very small so it is not possible to determine the mass of a single atom. So he focuses on the relative masses and create a table atomic mass (Figure 1.3) for the first time in human history. In the table, the mass of the lightest element, hydrogen adoption as a standard one (H = 1). Atomic mass is a relative value, meaning that a dimensionless ratio. Although several different atomic masses with modern values, most of the proposed values ​​in the range of compatibility with the current value. This shows that the idea and the experiment right.
Then the Swedish chemist Jons Jakob Berzelius Baron (1779-1848) to determine the mass of the oxygen atom as the standard (O = 100). Because Berzelius get this value based on the analysis of oxide, it has a clear reason to choose oxygen as standard. However, the standard hydrogen is clearly superior in terms of simplicity. Now, after much discussion and modification, carbon standard is used. In this method, the mass of 12C carbon with 6 protons and 6 neutrons is defined as 12.0000. Atomic mass is the mass of an atom relative to this standard. Although carbon has been declared as standard, this can actually be considered as a standard hydrogen is modified.
Atomic mass of almost all the elements very close to integers, ie integer multiples of hydrogen atomic mass. This is a natural kosekuensi fact that the hydrogen atom mass equal to the mass of a proton, which in turn is almost equal to the mass of a neutron, and electron mass is very small to negligible. However, most of the naturally occurring element that is a mixture of several isotopes, and atomic mass depends on the distribution of isotopes. For example, the atomic mass of hydrogen and oxygen is 1.00704 and 15.9994. The mass of the oxygen atom is very close to the value of 16 is a bit smaller.
Molecular mass and formula mass


Each compound is defined enumerated by a chemical formula that indicates the type and number of atoms menyususn compound. The mass formula (or formula mass) is defined as the sum of the atomic masses based on the type and number of atoms in the chemical formula defined. The chemical formula of molecules called molecular formula, chemical formula and mass is called the mass molekul.5 example, the molecular formula of carbon dioxide is CO2, and the molecular mass is 12 + (2x 6) = 44. As the mass of the atom, both mass and molecular mass formula should not be an integer. For example, the molecular mass of hydrogen chloride HCl is 36.5. Even if the type and number of atoms that make up molecules are identical, the two molecules may have different molecular masses when there are different isostop involved.


It is impossible to define molecules for compounds such as sodium chloride. Mass formula for sodium chloride is used instead of the mass molekular.d. Quantity of matter and mole


Quantitative methods most suited to express the amount of matter is the number of particles such as atoms, molecules that make up the material being discussed. However, to calculate the atomic or molecular particles are very small and can not be seen very difficult. Instead of counting the number of particles is directly the number of particles, we can use the mass of a certain number of particles. Then, how does a certain amount of numbers chosen? For


long story short, the number of particles in a 22.4 L of gas at STP (0 ℃, 1ATM) was selected as the standard amount. This number is called Avogadro's number. Name number Loschmidt also proposed to honor the Austrian chemist Joseph Loschmidt (1821-1895) who first with the experiment (1865).


Since 1962, according to the SI (Systeme Internationale) decided bahwam in the world of chemistry, mole is used as a unit of the amount of matter. Defined Avogadro's number of carbon atoms in 12 g 126C and renamed Avogadro constant.


There are several definitions of "mole":


(I) The amount of material that contains a number of particles contained in 12 g of 12C. (Ii) one mole of material that contains Avogadro constant number of particles.


(Iii) A material that contains 6.02 x 1023 particles in one mole.


e. Atomic mass units (sma)


Because the standard atomic mass is the mass of hydrogen Dalton system, standard mass in the right SI 1/12 the mass of 12C. This value is called the atomic mass unit (sma) and is equal to 1.6605402 x 10-27 kg, and D (Dalton) is used as a symbol. Atomic mass is defined as the ratio of the average sma elements with natural isotopic distribution with 1/12 sma 12C.

ATOMIC THEORY DEVELOPMENT & HIGH COORDINATION COMPOUNDS ( CH 2)

From the times of the ancient Greeks to the present, the model and the atomic theory continues to evolve. Through the model and theory of the atom, we can determine the structure of an atom. The development can not be separated from the efforts of scientists such as Democritus, John Dalton, JJ Thomson, Rutherford, Chadwick, ownership, Niels Bohr, Schrodinger, de Broglie and Heisenberg.
1. Atomic Theory Democritus (460 BC-370 BC)Democritus developed a theory of constituent materials. According to Democritus if a matter of a continuous cut would be obtained when the fundamental particles called atoms (Greek: atomos = not divided). This argument was rejected by Aristotle (384-322 BC), who argued that matter is continuous (material can be cut continuously until infinite). Aristotle's theory in favor Empedocles, that matter is made up of fire, water, earth and air. Around the year 1592 - 1655 Gasendi suggested that atom is the smallest part of a substance.2. Dalton Atomic Theory (1803)John Dalton reveals that:a. Atom is the smallest part of a substance.b. Simple spherical atoms are very small, can not be divided, created or destroyed.c. Same element contains the same atoms.d. Atoms have the same kind in every way, while the different atoms have different properties.e. Chemical reactions occur due to the merging and splitting of atoms.f. When atoms combine to form molecules. When atoms are joined together will form the molecular elements, whereas when atoms combine different molecular compounds are formed.Weakness of Dalton's atomic theoryIn the further development of the facts are found that can not be explained by this theory, among others:a. Unable to explain the electrical properties of the material.b. Unable to explain how atoms bond together.c. Dalton atomic model can not explain the difference between a single atom element with another element.These weaknesses can be explained after it was discovered some subatomic particles, such as electrons discovered by Joseph John Thomson in 1900, the discovery of proton particles by Goldstein in 1886.Excess Dalton's atomic theorya. Can explain the Law of Conservation of Mass (Lavoisier law)b. Still can explain Comparative Law (Law Proust)
3. Thomson Atomic TheoryBased on experiments on electrical conductivity through a vacuum tube / tube pengawan charge (discharge tube) or a cathode ray tube. In a cathode tube gas pressure inside the tube can be adjusted via the suction pump (vacuum pump). At sufficiently low pressure and high voltage (several thousand volts), the gas in the tube would glow with light colors depending on the type of gas in the tube (gas neon red, yellow sodium gas). If the gas pressure is reduced, then the area in front of the cathode will be dark. Dark areas will increase if the gas pressure in the tube continues to be reduced, eventually the entire tube to be dark, but the front of the cathode tube glow with a greenish tint.Through the experiments it can be shown that the perpendaran was caused by a radiation emanating from the surface of the cathode towards the anode. Because coming from the cathode, the radiation is called cathode rays. The results of the cathode tube experiment proves that there are negatively charged particles in an atom because the beam can be deflected toward the positive pole of the electric field. The next is a cathode ray particles and negatively charged particles, Thomson was named after the electron

 U.S. researchers have solved a note of the compound with the highest coordination number - number of the series of atoms that are able to bind. These compounds, thorium aminodiboranate, Th (H3BNMe2BH3) 4, has a core of 15 hydrogen atoms bind to separate thorium, breaking the previous calendar notes, which are held by other compounds, one by one.To obtain a high coordination number of an atom is surrounded by a great need of small atoms first, shown in a way that is not filled with atoms of one another. 'Both electronic factor and Steris - compaction - can limit the number of koordinasiannya, "said Gregory Girolami, from the University of Illinois at Urbana-Champaign, one of the team leaders. 'The thorium complex electronic factor and does not limit the amount of coordination is almost entirely dictated by compacting it.'High coordination number of a compound relies on thorium which becomes very large and the very small hydrogen atom. 'What we have done is to describe how to make a compound in which the thorium atoms form hydrogen bonds only with it, "said Girolami. There are only three other thorium compounds that can be set, but one of the coordination number is 12 and the rest of the other two remain unknown. "We also use a coordinating group which is compact and form a compound organic ligand, [so] binding on thorium atom with four hydrogen atoms on the purpose and features increased kestabilitasannya, 'explains Girolami.Thorium compounds representing 15 first coordinate complex (orange: Th, gray - brownish gray: B, purple: N, black: C, blue: H)While the new compounds have no immediate practical application, a high coordination number is very useful, says Girolami, in keeping the metal complex 'in isolation is good', which in turn will improve other properties such as vapor pressure, which is useful once in several applications such as disposition metal from the gas phase.Keith Izod, an expert on chemical coordination at Newcastle University in the UK, said, 'Although the determination of the amount of coordination can only be subjective, 15 coordinate thorium compounds were reported recently - this new press limit the maximum amount of coordination investigated so far.''This is a good structure which may be more than just suspicion than any chemical - although there is nothing wrong with that! Overall this is an interesting piece of work.