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Describe the thomson model of atom.??

Write the drawback of the Ruthorford's model..???

What iz Isotopes. Write three isotopes of hydrogen..???

Thomson model:

  • According to this model, an atom can be considered as a sphere of uniformly distributed positive charge in which there are electrons distributed symmetrically.

  • The electrons must be held by the positive charges by electrostatic forces. The mutual repulsions between the electrons are balanced by the force of attraction towards the centre of the sphere.

  • In an atom with a single electron like the hydrogen atom, the electron must be situated at the centre of the positive sphere.

  • In an atom with two electrons, like the helium atom, the two electrons must be symmetrically situated on opposite sides of the centre at a distance equal to half the radius of the positive sphere.

  • In the three-electron system, the electrons should be at the corners of a symmetrically placed equilateral triangle, the side of which is equal to the radius of the sphere.

  • Proceeding in this manner, Thomson could explain the arrangement of electrons ranging from 1 to 100 inside the positive sphere.

  • This model was also called 'the plum pudding model'. The electrons are like plums in a pudding (positive charge). The seeds in a watermelon fruit can be given as a parallel comparison.

  • With this model he tried to explain the observed spectra of elements.

  • According to him, the vibrations of electrons would give rise to electromagnetic energy radiated. He could explain with some success the process like chemical reaction, radioactivity etc.

Drawback of the Ruthorford 's model:

  • The model is applicable for one electron system.

  • According to Rutherford as the electron revolves around the nucleus it liberate energy regularly so when the electron loses all its energy it should fall in the nucleus which was impossible.

 

  • The model does not give the objection raised by Clerk Maxwell related to continuous emission of energy by electron.

  • The Rutherford’s model of atom does not say anything about the arrangement of electrons in an atom.

Isotope:

  • Isotopes are defined as atoms having the same atomic number, but different mass numbers. These atoms contain an equal number of protons and electrons, but a different number of neutrons.

For example, in nature, hydrogen is found in three forms with different mass numbers, namely protium (), deuterium(), and tritium (). These are the three naturally occurring isotopes of hydrogen. The atomic number of each isotope is 1, but the mass number varies i.e. it is 1, 2, and 3 respectively.

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 J.J. Thompson's model of the atom was also known as---

1- Christmas cake model
2- Watermelon model
3- Plum pudding model 
Because as in Christmas cake model dry fruits is refered to electrons and the cream refered to positively charged sphere.
 

The Rutherford’s model of atom does not say anything about the arrangement of electrons in an atom.

The atoms were not stable as he has not shown stability. This was a major drawback.

 

Each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei 

1H, 2H, and 3H are isotopes of hydrogen


 

 

 

 
 
And same in the other two.  
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1.

  1. in thomsons model ,the following postulaes have been proved

  2. An atom consists of a positively charged sphere with electrons embedded in it.
  3. The negative and positive charges present inside an atom are equal in magnitude. Therefore, an atom as a whole is electrically neutral.

 

  1. Thomson’s model of the atom is also known as the plum pudding model.

Figure: Thomson’s model of the atom.

2.

Drawbacks of the model...

  • The model is applicable for one electron system.
  • According to Rutherford as the electron revolves around the nucleus it liberate energy regularly so when the electron looses all its energy it should fall in the nucleus which was impossible.
  • The model does not give the objection raised by Clerk Maxwell related to continuous emission of energy by electron.
  • The Rutherford’s model of atom does not say anything about the arrangement of electrons in an atom.

  3.

Isotopes are defined as atoms of same element having the same atomic number, but different mass numbers. These atoms contain an equal number of protons and electrons, but a different number of neutrons.

For example, in nature, hydrogen is found in three forms with different mass numbers, namely protium (), deuterium(), and tritium ( ). These are the three naturally occurring isotopes of hydrogen. The atomic number of each isotope is 1, but the mass number varies i.e. it is 1, 2, and 3 respectively. Some other examples of isotopes include C- 12 and C-14, which are isotopes of carbon, and Cl-35 and Cl-37, which are isotopes of chlorine.

thumbs up plz!

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