Scientific Fact 3

                                                            Theory of Atom

Democritus (460 BC-370 BC)

   

Previously I've discussed the particles matter about atom. This time I will discuss the theory of the atomic scientists. They argue with each other until finally getting the correct conclusion, here is the opinion of the scientists.
 

 In the 4th century BC a Greek philosopher named Democritus proposed the opinion that "all matter can be broken into small particles that can not be broken again. Such particles called atoms" (from the a = no and Tomos = divided). So, atom is the smallest part of a substance that can not be divided up again.

John Dalton (1766-1844)

 Approximately 2000 years later, in 1803 a chemist named John Dalton proposed the atomic theory of challenge known as "Dalton Atomic Theory" which says:

1. Every material is composed of the smallest particel called atom.

2. Atom can't be subdivided to smaller particles with similar characteristic.

3. Atoms from certain element have the same characteristic and mass. Different elements have same atoms

 having different mass.

4.  A compound is composed of 2 or more different atom types.

5. Chemical reaction is the event of atom separation or incorporation from element or compound. 
Dalton's atomic theory has a weakness that is can not explain the differences in atoms and molecules. 

Joseph John Thompson (1856-1940)

 In 1906, a physicist named J.J. Thompson suggests that the "atom is a small ball on the surface positively charged negatively charged electrons scattered".

According to Thompson,"the atom is neutral because the amount of positive charge equal to the negative charge". Weakness  Thompson theory was not able to explain the position of the electrons in the atom.

    
 Another scientist, Ernest Rutherford, successfully abort Thompson atomic theory. According to Rutherford, "the atom consists of positive charges that build up in the middle of the atom called the nucleus. Around the atom, electrons circulate around it". Weaknesses of Rutherford's theory is not able to show the stability of the electron around the nucleus.

Ernest Rutherford (1871-1937)

  

    Problems on Rutherford atomic theory solved by Bohr Atomic theory, which states:
1. Atom consists of a positively charged nucleus with electrons moving around the nucleus at a particular track.
2. Electrons in the trajectory does not absorb or emit energy.
3. When electrons move trajectory, there will be a change in energy.
     Based on the discovery of some scientists, Edwin Schrodinger proposed the modern atomic model, which takes into account the wave nature of electrons. According to this theory, the atom has a positive charge that is located in the central part, with the electrons are not in a fixed orbit.

"That's is the theory of some scientists about atom, please give your comment"