Dalton's Atomic Theory

Dalton's Atomic Theory

TOPICS: Dalton's Atomic Theory

 

Dalton's Atomic Theory

 

Today the word atom never mind very often we hear. But the birth of the concept of atoms requires a very long time, more than 2000 years. After his birth, still needed several centuries to finalize this concept. Atoms are initially we consider to be a solid ball that hard, now it turns out we understand as a cloud of matter is complicated.

In the 5th century BC, two Greek philosopher Leucippus and his pupil Democritus, stroll along the Aegean coast. Leucippus take his students to ponder something: "Is not the sea that seems to be continuously composed of small grains such as sand that lay on the beach? From a distance the sand looks continuous but close observation shows the sand composed of fine granules ".

Democritus who lived between the years 470 to 380 BC developed the idea of ​​the teacher. He stated that the matter is composed of smallest particles called atoms (a = not, Tomos = split). He believes that the atoms of different elements have different shapes and sizes. Water has the form a smooth ball that was cool while having the form of a sharp fire so hot. At that time, the Greeks believed that there are four elements that make up nature, namely earth, water, fire, and air. Nevertheless, thought Democritus did not attract people for 2,000 years because they have an addiction theory that matter is continuous.

In about 1779 a French scientist, Antoine Laurent Lavoisier, experiment carefully, namely mercury and the metal heats the air in a sealed tube. From these experiments he concluded that "in any chemical reaction, mass quantities of substances before and after the reaction is the same". This conclusion was later known as the Law of Conservation of Mass. Twenty years later, another French scientist who settled in Madrid, Joseph Louis Proust formulated a law called the Law of Comparative Keep reading: "Comparison of mass elements that compose a substance always remains".

To explain these two laws, a high school teacher of English, John Dalton, evoke memories of people about a term that has been forgotten that the atom. Dalton promoted his new theory of the atom through his book entitled New System of Chemical Philosophy. Beads of Dalton's atomic theory is as follows.

1. The material is composed of the smallest particles called atoms.

2. Atoms can not be subdivided into smaller particles.

3. The atoms of an element have the same nature and mass.

4. Different elements have atoms of different mass and properties.

5. The chemical reaction is the splitting or merging or rearrangement of atoms.

So it is clear now how Dalton's atomic theory capable of explaining both the above theory. In regard to the Law of Conservation of Mass, a chemical reaction just involve the rearrangement of atoms reactant into reaction products, so the mass number should remain the same. Or in other words, during the reaction the atoms are not created and destroyed. In regard to Comparative Law Still, a compound formed or composed of different types of atoms with a certain ratio so as to have a mass ratio always remains.

However, that does not mean Dalton's atomic theory has been perfect. Atoms in the form of solid ball of course not able to explain why a particular solution is electrolyte alias can conduct electricity. In fact, some parts of this theory is proven wrong.

Scrutiny began late 19th century until the early 20th century, drove the experts to the conclusion that atoms can be broken down into particles smaller. Subatomic particles are positively charged protons, neutral neutrons, and electrons are negatively charged. Thus points to the 2nd of this theory wrong.

Atom has a number of specific protons and electrons. But the atoms of the same element can have different numbers of neutrons. This causes the atoms of the same element may have different masses. These are called isotopes. This proves that point all three of Dalton's atomic theory is also wrong.

Apart from the various errors in his theory, Dalton has laid the foundations of modern atomic theory. This theory is built on a variety of experimental data that had been done by other experts such as Lavoisier and Proust.

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