MODERN ATOMIC THEORY

1. Planck's Quantum Theory of Radiation
In 1900 Planck proposed the quantum theory which states that the energy of an object can only be changed (increased or decreased) by a multiple of a unit of energy called quantum. Planck's law states that a quantum of energy is not fixed, but depends on the frequency of radiation.

E = h . v 

E = quantum energy (joule)

h = Planck constant (6,625 x 10^–34 joule sekon)

v = frequency radiation (sekon^–1)

ν = c / λ 

c = speed of light (3 x 10⁸ m.sekon^–1)

λ = wavelength (m)

Planck's law can be written in the form :  

E = (hc) / λ

2. Bohr Atomic Theory

Bohr's atomic theory dotted starting on the following assumptions.

1. Electrons surrounding the nucleus is at the energy level (trajectory) specific, so the electrons also have a certain energy.
2. Contrary to the theory of Maxwell's electrodynamics, for electrons moving in the trajectory does not emit energy in the form of radiation.
3. Electrons can move from energy level (path) to a low energy level (trajectory) is higher when the electron absorbs energy and vice versa can be moved from the energy levels (path) to a high energy level (trajectory) is lower when the energy release.

 

Figure 1.3 Bohr atom theory 

example:
- Track I have the energy level E1
- Scenic II has the energy level E2
- Track III has the energy level E3 and beyond
The amount of energy absorbed or emitted can be calculated from the following quantum theory.

DE = E2 – E1 = h v =(hc) / λ 

3. Modern Atomic Theory 

Now we will study the development of modern atomic theory based on the concept of wave mechanics. In 1900, Max Planck (1858-1947) suggested that light waves have particle properties, and the transfer of a direct air-electromagnetic radiation in the package or unit of energy called a quantum (asked in the Latin word which means what?). Planck's theory was proven by Albert Einstein (1879-1955) in 1905, who testified that the light waves composed of photons. Then in 1923, Louis de Broglie (1892-1987) explains that a particle, such as electrons, it has wave properties. Based on the concept of wave particle duality, the Erwin Schrodinger (1887-1961) and Werner Heisenberg (1901-1976) in 1926 suggested that the position or location of an electron in an atom can not be determined exactly. We can only ensure the possibility of the location of the electron. As an analogy, on a fan (fan) which is being spun seen that the leaves of the fan that fills the entire field. We can not ensure that the location of a piece of fan blade at a given moment, but we can easily make sure where he might be found. Modern atomic theory explains that elektronelektron the atom occupies a space or "cloud" so-called orbital, which is the space where electrons are most likely to be found. Orbital is a certain energy levels in atoms. In 1928, Wolfgang Pauli (1900-1958) suggested that each orbital can accommodate a maximum of two electrons. Electrons move around the nucleus in energy levels or specific skins. To compensate for the repulsive force between them, two electrons in one orbital is always rotated in the opposite direction. Some orbitals combine to form a group called the subshell. Subshell joined to form the skin. One is composed of skin-subshell subshell. Composed of a single subshell orbitals. Accommodate a maximum of two-electron orbital. 

  

My Question

Contrary to the theory of Maxwell's electrodynamics, for electrons moving in the trajectory does not emit energy in the form of radiation. Based on these quotations in the form of electrons emitted? 

4. Atom model of quantum mechanics

Atom model of quantum mechanics developed by Erwin Schrodinger (1926). Before 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 carefully at the same time, which can determined is the probability of finding an electron at a certain distance from the nucleus ".  

Region of space around the core with the probability for electrons called orbitals. Shape and orbital energy levels defined by the Erwin Schrodinger Schrodinger.Erwin solve an equation for the wave function to describe the discovery of a possible limit of the electron in three dimensions. 

Schrodinger equation

x, y and z = Position in three dimensions
Y = Wavefunction
m = mass
ђ = H/2p where h = Plank constant, and p = 3.14
E = Total energy
V = Potential energy

Model of the atom with the orbital path of electrons is called the modern atomic model or atomic model of quantum mechanics is valid until today, as shown in the image below.

Current model of the atom or atomic model wave mechanics

 Shows the electron cloud around the nucleus where the probability of an electron. Orbitals describing the electron energy levels. Orbitals with energy levels of the same or nearly the same will form the sub-skin. Some sub-skin leather combine to form kulit.Dengan thus consists of several sub-skin and consists of several orbital subshell. Although the skin is the same position but not necessarily the same orbital position.

SPECIAL FEATURES MECHANICAL WAVE ATOM MODEL

1. The movement of electrons have wave properties, so 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 shape darikebolehjadian greatest discovery of the electron with an atom in certain circumstances).
2.  Orbital shapes and sizes depending on the price of the three numbers kuantumnya. (The electrons occupying the orbital quantum number is expressed in)
3.  Position as far as 0.529 electrons from the core H Armstrong by Bohr instead of something definite, but probable discovery of the electron is the greatest opportunity.

Chadwick trial

 

Weakness Modern Atom Model

Schrodinger wave equation can only be applied exactly to the particle in a box with a single electron and atom
 

MID TEST

UTS 21 November 2011

1.      pure substance X is solid at room temperature. if the substance is heated to 230 ℃ is melted gradually. if then cooled to room temperature, the liquid can not be frozen.

a)      is it possible X of an element or a compound. explain it!

answer :          X is a compound. The compound is a collection of several elements. If a compound in the melt by the heat will melt easier. But it will be difficult molten liquid solidifies at the same temperature setting before him in the melt. If you want to make it freeze then the need is even lower temperatures. It may be a temperature below 0 ℃.

b)      does it a chemical change occurred ? if so can it be said to undergo an endotherm changing, based on the information provided?

answer :          chemical changes that occur can be called endothermic reactions. Endothermic reaction is a reaction that is accompanied by heat transfer from the environment to the system (heat absorbed by the system from its environment); characterized by a decrease in ambient temperature around the system. Substance X which initially are solid when heated at a temperature of 230 ℃ to melt in the heat in the environment caused due to move to the substance, so that the substance to be melted and the temperature in the substance becomes higher than

the temperature of their environment.

c)      Can it be said that the liquid is an element, based on the information provided.

answer :             there are elements which are in fluid. For instance mercury. But based on the information that is given me to say that it's open compound elements.

2.      When a candle that weight 10 g is burned in oxygen, carbon dioxide and water vapor formed by combustion the weight more than 10 g. was this case match with the law of conservation of mass.

answer :             law of conservation of mass says that the mass before and after the reaction is the same. The mass of wax in the fuel will be equal to the mass of wax before the fire. The melted wax is still wax, which changed its form only. Candles will be burning the gas and the amount of energy (heat and light). If the result of burning accommodated and weighed, surely its mass equals the mass plus the mass of oxygen candles are used on burning it.

3.      When carbon burns in oxygen under limited number, it will form two gaseous compounds. Suggest the way to differentiate the two compounds with one another.

Answer :              How to distinguish the two compounds with one another by adding a non-polar compounds or compounds that make reaching saturation point state.

4.      After medelev compiled the periodic table, he conclude that the atomic weight of certain element was wrong ruling, and this conclusion was apparently correct. How mendelev was able to predict that several atomic weight were wrong ? why his prediction are not always right?

Answer :          In 1869, Dmitri Ivanovich Mendeleyev Russian chemist nationality arrange 65 elements known at that time. Mendeleev sort the elements of increasing atomic mass and chemical properties

At the same time, Julius Lothar Meyer made ​ ​arrangement of elements such as the dikernukakan by Mendeleyev. Only, Lothar Meyer arrange these elements based on their physical properties. Although there are differences, but both produce the same grouping of elements.

Mendeleyev provide an empty box to place the elements that time it has not been found, such as elements with mass numbers 44, 68, 72, and 100. Mendeleyev had predicted the properties of elements and it is a prophecy after the elements were found. Arrangement of the elements of Mendeleev perfected under the law and called Mendeleev periodic system.

Mendeleev periodic system consisting of groups (elements located in a single column) and period (the elements which lie on one line)

               

5.      When an aqueous solution of merkuri chloride is added to an aqueous solution of silver nitrate, a white solid forms. Identify the white solid and write the balanced equation for the reaction that occurs.

Answer :          HgCl₂ + 2AgNo₃ àHg(No₃)₂ + 2AgCl

White solid : AgCl