E. Rutherford is one of the famous scientist of nuclear physics, he is also known as father of nuclear physics. He was born at Spring Grove on August 30,1871. He got nobel prize in 1908 in chemistry. He is famous for discovery of nucleus of an atom with the gold foil experiment and for his work on chemistry. He is better known as Rutherford.
How Rutherford give his theory on atom.
Rutherford was very interested in knowing 'how the electrons are arranged within the atom. In his experiment, fast moving alpha particles were made to fall on a thin gold foil.
◆ Rutherford take gold foil because he wanted as thin a layer as possible. And we know that gold is more meliable than any other metal. So, he took gold as foil. The gold foil that he had taken is about 1,000 atom thick (means the thickness of gold foil is equal to 1,000 atom which is arranged along straight line).
◆ Alpha particles are doubly-charged helium cons. They have mass of 4U, the moving alpha particles have a considerable amount of energy.
◆ Rutherford expected that alpha particles would be deflected by the sub-atomic particles in the gold atoms. Since the weight if alpha particles is more than protons, Rutherford did not expected to see large deflections. And, the alpha particles scattering experiment gave the hundred percent unexpected results which expects by Rutherford.
What observed by Rutherford with Gold foil experiment:
1) Most of the fast moving alpha particles passed straightly through the gold foil.
2) Very few of them were deflected by the foil by small angles (acute angles).
3) it's about 1 out of every 12,000 particles rebound at some angle.
The following points Rutherford concluded after his alpha particles scattering experiment :
1) Most if the space inside the atom is blank because he observed that most of the alpha particles passed through the atom. So, he think that the most of the space inside the atom is not containing anything.
2) Very few of them were deflected from their path, this indicating that the positive charge of atom occupies some space.
3) Little of them are deflected at the angle of 180°, this is indicating that all positive charge and mass of gold atom were concentrated as very small volume inside the atom.
According to Rutherford negatively charged electrons revolve around the positively charged electron, like planets revolving around the Sun in this case the revolving electrons continuously change the direction of their velocity at every point of circular path. It means the electrons revolving around the nucleus are accelerated charged particles. According to classical electromagnetics accelerating charged particles radiate energy in form of electromagnetic waves. It means the revolving electrons should radiate energy, If it really happens the orbital energy of the revolving electrons will coulntinuosly go on decreasing and finally with decreasing radius electrons will fall in to the nucleus. That is the atomic volume should get reduce to negligibly small value. But actually it not happen hence it was concluded that 'Rutherford's atom model' stating about planetary motion of electrons is not correct.
Remodification of 'Rutherford's atom model'.
After that Neils Bhor gave the suitable concept after modifing 'Rutherford's atom model'.
He gave the following postulates :
I. Electrons are revolving around the nucleus in a difinite circular path ( Call as 'Orbit' or 'Shells' ).
II. Each orbit is associated with different amount of energy, known as energy level of the orbit.
III. A energy is either radiated or observed in form of electromagnetic radiation. When electrons jump from one orbit to another orbit.
IV. The energy will go on increasing as they move away from the nucleus.
V. The number of electrons in each orbit can governed by the formula '2n^2'
In 1913, after remodification of 'Rutherford's atom model', Bohr points these terms.
I. Electrons are revolving around the nucleus in a difinite circular path ( Call as 'Orbit' or 'Shells' ).
II. Each orbit is associated with different amount of energy, known as energy level of the orbit.
III. A energy is either radiated or observed in form of electromagnetic radiation. When electrons jump from one orbit to another orbit.
IV. The energy will go on increasing as they move away from the nucleus.
Bohr gave name to the orbits as K, L, M, N and so on with increasing distance from nucleus energy of orbits goes on increasing from negative value towards zero.
Neils Bohr decided the maximum numbers of holding capacity by each orbits in terms of formula "2n²" where "n" is the number of orbits starting from nucleus. That is maximum of two electrons can be accommodated in the first orbit.
It means in "K" Orbit a maximum of eight electrons can be accommodated.
[ ie : For "K" orbit n = 1 hence, 2n² = 2 × 1² = 2. ]
It means in "L" Orbit a maximum of eight electrons can be accommodated.
[ ie : For "L" orbit n = 2 hence, 2n² = 2 × 2² = 8. ]
That is in "M" orbit a maximum of eighteen electrons can be accommodated. [ ie : For "M" orbit = n = 3 hence, 2n² = 2 × 3² = 18
And for "N" orbit maximum of thirty two electrons can be accommodated.
[ ie : For "N" orbit = n = 4 hence, 2n² = 2 × 4 × 4 = 32. ]
It means in "N" orbit a maximum of 32 electrons can be accommodated.
How Rutherford give his theory on atom.
Rutherford was very interested in knowing 'how the electrons are arranged within the atom. In his experiment, fast moving alpha particles were made to fall on a thin gold foil.
◆ Rutherford take gold foil because he wanted as thin a layer as possible. And we know that gold is more meliable than any other metal. So, he took gold as foil. The gold foil that he had taken is about 1,000 atom thick (means the thickness of gold foil is equal to 1,000 atom which is arranged along straight line).
◆ Alpha particles are doubly-charged helium cons. They have mass of 4U, the moving alpha particles have a considerable amount of energy.
◆ Rutherford expected that alpha particles would be deflected by the sub-atomic particles in the gold atoms. Since the weight if alpha particles is more than protons, Rutherford did not expected to see large deflections. And, the alpha particles scattering experiment gave the hundred percent unexpected results which expects by Rutherford.
What observed by Rutherford with Gold foil experiment:
1) Most of the fast moving alpha particles passed straightly through the gold foil.
2) Very few of them were deflected by the foil by small angles (acute angles).
3) it's about 1 out of every 12,000 particles rebound at some angle.
The following points Rutherford concluded after his alpha particles scattering experiment :
1) Most if the space inside the atom is blank because he observed that most of the alpha particles passed through the atom. So, he think that the most of the space inside the atom is not containing anything.
2) Very few of them were deflected from their path, this indicating that the positive charge of atom occupies some space.
3) Little of them are deflected at the angle of 180°, this is indicating that all positive charge and mass of gold atom were concentrated as very small volume inside the atom.
According to Rutherford negatively charged electrons revolve around the positively charged electron, like planets revolving around the Sun in this case the revolving electrons continuously change the direction of their velocity at every point of circular path. It means the electrons revolving around the nucleus are accelerated charged particles. According to classical electromagnetics accelerating charged particles radiate energy in form of electromagnetic waves. It means the revolving electrons should radiate energy, If it really happens the orbital energy of the revolving electrons will coulntinuosly go on decreasing and finally with decreasing radius electrons will fall in to the nucleus. That is the atomic volume should get reduce to negligibly small value. But actually it not happen hence it was concluded that 'Rutherford's atom model' stating about planetary motion of electrons is not correct.
Remodification of 'Rutherford's atom model'.
After that Neils Bhor gave the suitable concept after modifing 'Rutherford's atom model'.
He gave the following postulates :
I. Electrons are revolving around the nucleus in a difinite circular path ( Call as 'Orbit' or 'Shells' ).
II. Each orbit is associated with different amount of energy, known as energy level of the orbit.
III. A energy is either radiated or observed in form of electromagnetic radiation. When electrons jump from one orbit to another orbit.
IV. The energy will go on increasing as they move away from the nucleus.
V. The number of electrons in each orbit can governed by the formula '2n^2'
Bohr's Atom Model in detailed
In 1913, after remodification of 'Rutherford's atom model', Bohr points these terms.
I. Electrons are revolving around the nucleus in a difinite circular path ( Call as 'Orbit' or 'Shells' ).
II. Each orbit is associated with different amount of energy, known as energy level of the orbit.
III. A energy is either radiated or observed in form of electromagnetic radiation. When electrons jump from one orbit to another orbit.
IV. The energy will go on increasing as they move away from the nucleus.
Bohr gave name to the orbits as K, L, M, N and so on with increasing distance from nucleus energy of orbits goes on increasing from negative value towards zero.
Neils Bohr decided the maximum numbers of holding capacity by each orbits in terms of formula "2n²" where "n" is the number of orbits starting from nucleus. That is maximum of two electrons can be accommodated in the first orbit.
It means in "K" Orbit a maximum of eight electrons can be accommodated.
[ ie : For "K" orbit n = 1 hence, 2n² = 2 × 1² = 2. ]
It means in "L" Orbit a maximum of eight electrons can be accommodated.
[ ie : For "L" orbit n = 2 hence, 2n² = 2 × 2² = 8. ]
That is in "M" orbit a maximum of eighteen electrons can be accommodated. [ ie : For "M" orbit = n = 3 hence, 2n² = 2 × 3² = 18
And for "N" orbit maximum of thirty two electrons can be accommodated.
[ ie : For "N" orbit = n = 4 hence, 2n² = 2 × 4 × 4 = 32. ]
It means in "N" orbit a maximum of 32 electrons can be accommodated.
