Entropy

Entropy is a driving force that affect spontaneous process either it is exothermic or endothermic. It is a thermodynamic state quantity for measuring the randomness of the molecules. In early it was believed that in an exothermic process internal energy changes spontaneously. But after a period of time it have been prove that in endothermic process spontaneously internal energy may changes. Just for example, melting of ice is an endothermic process.. Ice melts spontaneously. Entropy is expressed as S. The change in entropy is found by the subtraction of initial entropy from final entropy. There have a limitation in the physical definition of entropy in classical thermodynamic. To overcome this limitation there need a numerical definition of entropy. In 1850 Clausius gives a numerical definition of entrop y. According to Clausius, entropy is a constant value of a system if there have no role of heat. Hence, it is clear that heat have an impacts on entropy. If heat flows into a system, entropy changes of this system. The changes of entropy is  expressed as heat divided by temperature. The absolute entropy of a substance at standard temperature and pressure is called standard entropy. It is also called absolute entropy. The unit of entropy is expressed as eu that is calories per degree per mole.

Chemical reaction

Chemical reaction is a process by which two or more chemical compounds reacts with each other or a single chemical compound restructures os dissociates and finaly produce a new compound. The new product is called product of the chemical reaction and the substance that take place in reaction is called reactant. For example, let Hydrochloric acid and sodium hydroxide is are reactants of a chemical reaction. After a reaction these reactant produces sodiam chloride and water. It is an example of neutralization reaction.Reaction can be classified into following class. These are addition reaction, substitution reaction, redox reaction, dissociation reaction etc.

Spontaneous process

Spontaneous process can be defined as things happening naturally without any external force concerning. Spontaneously process in physical chemistry is very important to know. In an opposite view, the process that is not concerned with naturally happening, but occurs by an external force is a non spontaneous process. The heat will flow higher temperature to lower temerature., it is a natural process. There need an external force to flow heat from lower temperature to higher temperature.Rolling of a ball from top of the hill to botom is a naturalprocess. But picking ball from botom to top is not natural.

Thermochemistry

Thermochemistry is a study of thermal and heat change in chemical reaction. The including topics of thermochemistry is internal energy of a substance, exothermic chemical reaction and endothermic chemical reaction. Internal energy is the processed energy by any substance. It can not measure for a substance. But in a chemical reaction the changes in internal energy can be measure. The change of internal energy of a chemical reaction determines that the reaction will be exothermic or endothermic reaction. If in a chemical reaction, the changing of internal energy is positive then the reaction is exothermic. But, the change of internal energy if negative then chemical reaction is termed as endothermic chemical reaction. Positive value of internal energy indicates the reaction will will absorb energy from surrounding. Because, in this case products internal energy is higher than reactant internal energy.

Chemical kinetics

Chemical kinetics is the important part of chemistry that deals with the rate of a chemical reaction. It is a study of chemical reaction rates, rate law, factors affacting on chemical reaction, such as temperature, concentration and pressure. Mechanism of the reaction is also a topics of chemical kinetics. In a reaction converting reactant into product happens spontaneously. In such spontaneous process reactant starts to convert into product. This conversion of reactant into product happens in a different rate for different reactant and product. Some reactions are slow and others are fast. The example of a slow chemical reaction is rusting of iron. It takes years of time. On the other hand reaction of water with sulfuric acid is a fast reaction. In different temperature same reactant shows different reaction rate. Same things happens in different

Transition state

A chemical reaction happend in a simultaneous process that is start of breaking of one bond and forming of another bond. This two process happens concurrently. Simply to say one bond is breaking and another bond is forming. With an advancement of this process there found an intermediate state where there have highest energy and form a structure of odd compound . This is not a real molecule. It's next step is the final product. Here leaving atom is adjunct to the central atom with paetial bond and new atom is also that.

Solar system atomic model

Rutherford's atomic model

 To define the atom and atomic structure Rutherford proposed a model of atom that can explain the structure of atom. Though, this model have a few drawbacks, but it was the first acceptable model of atom. Rutherford's atomic model is the modified result of a world re known experiment to know the behaviour of alpha particles that is known as Rutherford's alpha particle scattering experiment. Rutherford and Marsden done an experiment that shows a significant alpha particles scattering through atom. This experiment of alpha particle scattering gives most of the idea of atomic structure that leads to  a modern model of atom latter.

Rutherford's alpha particle scattering experiment

 Human thirst of innovation was started from the primitive time of human origin. A one discovery of science leads scientists to drive for new discovery. After the discovery of smaller constituents of atom, electron, proton and neutron, scientists are aggressive to know that how these three particles located with the atom and what is the rearrangement of these particles within atom. To discover this Rutherford and Marsden done an experiment that is known as Rutherford's alpha particle scattering experiment. Alpha particle scattering experiment enables them to get a few idea about the structure of atom and the locality of electron and proton. Next it enable to give a model of atom that is known as Rutherford's atomic model  in which major statements of the atomic model comes from alpha particles scattering experiment.

Alpha particles scattering experiment is done by passing of alpha particles through thin gold foil. The direction of the alpha particles pass through are found in different direction. Few particles did not deflected, few particles showed a large deflection and some showed little deflection. Very wonder they observed that a little amount of alpha particles did not pass through the goil foil and returned back.

 From the result of the alpha particles scattering there found some idea about atomic structure and probably the location of the particles within atom. Though, alpha particle is positively charged, the deflection of alpha particle indicates that something positively charged particles exist near, from where alpha particles started to deflecting. Among the three constituent particles of atom proton is positively charged, electron is negatively charged and neutron is charge neutral. Hence, among the particles it should be proton that is responsible of alpha particle deflection. The alpha particles passing way that is more near to protons location that shows more deflection. The alpha particles that moves directly toward the centre of the atom that returns back and do not pass through. This indicates that the centre of the atom is dense and rigid. This is called nucleus consist with proton, neutron and other particles. A large number of alpha particles pass through the gold foil without any deflection. That proves that the atom have a large volume of empty.

 This alpha particle scattering experiment provides a wide range of information to establish an atomic model, but not sufficient.

 To give a complete model of atom, Rutherford tries to make a relationship of planets orbiting surrounding the sun. Hence, to describes the atomic model Rutherford take into consideration of Johannes Kepler's model of solar system by
 considering the atom with the behaviour of sun and its planet.

 Simpled form of Rutherford's solar system atomic model

The atomic model of Rutherford says that the electron in an atom is moving surrounding the nucleus, just like how the planets are moving surrounding the sun by an elliptical path. The electrons are in negatively charged and the nucleus is positively charged. All of the mass of an atom is concentrated in nucleus. Comparing with the volume of whole atom the volume of nucleus is negligible. The whole atom is electrically neutral, because the number of electron surrounding the nucleus is equal to the number of proton in nucleus.

 Evidence of Rutherford's atomic model

Not only the alpha particle scattering experiment is a strongest evidence of accepting most of the parts of Rutherford's atomic model. In modern science there have a wide range of evidence in favour of most of the statements of Rutherford's atomic model to accept. Few statements are very Wonder found that these are significantly coping the the theory of relativity.


Rutherford's atomic model shows that the total mass of atom is concentrated into nucleus. But if we agree about the statement we have to agree that the mass of electron is negligible or zero. But electron also a particle. If other particles such as proton and neutron will contain mass, why electrons mass will be zero? Einstein's theory of relativity shows us that mass is relative with speed, space and position. Consider an analogy that you bind a substance with a rope and hold another side of the rope with your finger. Start to moving your hand in rotational pattern. The dense substance that is bonded with rope will started to rotate surrounding the point. Very wonder the rotating substance will gradually changes its position in space. With the increasing of speed of rotation it will tends to gradually moving to upward. That indicates something overcoming the attraction of earth on the substance. Besides of vector role, there acts another factors which is theory of relativity. Something that will move more speed its mass will be more less. If some matter or particles achieve speed.

 Limitation of Rutherford's solar system atomic model

 With the emergence of electrodynamic theorem, it proves that with the spending of time electron will release energy and will become closer to nucleus spirally and ultimately it will fall into nucleus. Wave mechanics also shows that electron have two nature. These are particle nature and wave nature. These two nature suggested that electron will not move by an elliptical path. On the other hand, according to Neils Bohr, the electron will jump to lower energy state to higher energy state and higher to lower energy state. Hence it will create spectrum by absorbing and emitting energy.

 If we put Rutherford's atomic model with Plank's quantum theory of radiation, there we will find complexity. Plank's quantum theory of radiation does not support  Rutherford's atomic model.