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Statement-I : In Rutherford's gold foil ...

Statement-I : In Rutherford's gold foil experiment, very few `alpha`-particles are deflected back.
Because
Statement-II : Nucleus present inside the atom is heavy.

A

Both 'A' and 'R' are true and 'R' is the correct explanation of 'A'.

B

Both 'A' and 'R' are true and 'R' is not the correct explanation of 'A'

C

'A' is true and 'R' is false

D

'A' is false and 'R' is true

Text Solution

Verified by Experts

The correct Answer is:
B
Most of the particles move without any deflection. This is because most of the space inside the atom is empty. Some of the the particles get deflected through small angles, this shows the presence of the positive charge concentration in the centre of each atom i.e the nucleus.
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Assertion (A) : In rutherford's gold foil experiment, very few alpha particle are deflected back Reason (R ) : Nuclear present inside the atom is heavy

Assertion : In Rutherford's alpha -particle scattering experiment, most of the alpha -particles were deflected by nearly 180^(@) . Reason : The positive charge of the atom is spread throughout the atom that repelled and deflected the positively charged alpha -particles.

Rutherford model: The approximate size of the nucleus can be calculated by using energy conservation theorem in Rutherford's alpha -scattering experiment. If an alpha -particle is projected from infinity with speed v towards the nucleus having Z protons, then the alpha -particle which is reflected back or which is deflected by 180^@ must have approached closest to the nucleus .It can be approximated that alpha particle collides with the nucleus and gets back. Now if we apply the energy conservation equation at initial point and collision point then: (P.E.)_i= 0 , since P.E. of two charge system separated by infinite distance is zero. Finally the particle stops and then starts coming back. 1/2m_alpha v_alpha^2+0=0+(Kq_1q_2)/Rimplies 1/2m_alphav_alpha^2=K(2exxZe)/R implies R=(4KZe^2)/(m_alphav_alpha^2) Thus the radius of nucleus can be calculated using above equation. The nucleus is so small a particle that we can't define a sharp boundary for it Radius of a particular nucleus is calculated by the projection of alpha -particle from infinity at a particular speed. Let this radius is the true radius . If the radius calculation for the same nucleus is made by another alpha -particle with half of the earlier speed, then the percentage error involved in the radius calculation is :

Rutherford model: The approximate size of the nucleus can be calculated by using energy conservation theorem in Rutherford's alpha -scattering experiment. If an alpha -particle is projected from infinity with speed v towards the nucleus having Z protons, then the alpha -particle which is reflected back or which is deflected by 180^@ must have approached closest to the nucleus .It can be approximated that alpha particle collides with the nucleus and gets back. Now if we apply the energy conservation equation at initial point and collision point then: (P.E.)_i= 0 , since P.E. of two charge system separated by infinite distance is zero. Finally the particle stops and then starts coming back. 1/2m_alpha v_alpha^2+0=0+(Kq_1q_2)/Rimplies 1/2m_alphav_alpha^2=K(2exxZe)/R implies R=(4KZe^2)/(m_alphav_alpha^2) Thus the radius of nucleus can be calculated using above equation. The nucleus is so small a particle that we can't define a sharp boundary for it An alpha -particle with initial speed v_0 is projected from infinity and it approaches up to r_0 distance from a nuclie. Then, the initial speed of alpha -particle, which approaches upto 2r_0 distance from the nucleus is :

Statement -1 : Large angle scattering of alpha particles led to the discovery of atomic nucleus. Statement -2 : Entire positive charge of atom is concentrated in the central core.

Statement-I : No two electrons in an atom can have the same values of four quantum number. Because Statement-II : No two electrons in an atom can be simultaneously in the same shell, same subshell, same orbitals and have same spin.

Assertion : During alpha -particles scattering experiment, 99% of the alpha -particles get deflected through very large angles. Reason : The nuclei of atoms are positively charged and repel alpha -particles which are also positively charged.

In the gold foil experiment of Geiger and Marsden, that paved the way for Rutherford's model of an atom, ~ 1.00% of the alpha -particles were found to deflect at angles gt 50^(@) . If one mole of alpha -particles were bombarded on the gold foil, compute the number of alpha -particles that would deflect at angles less than 50^(@) .

Assertion: In Rutherford's experiment, a-particles from a sodium source were allowed to fall on a 104 mm thick gold foil. Most of the particles passed straight through the foil. Reason : The entire positive charge and nearly whole of the mass of an atom is concentrated in the nucleus.

Which of the following statement about Rutherford's model of atom are correct? (i) Considered the nucleus as positively charged. (ii) Established that the alpha -particles are four times as heavy as a hydrogen atom. (iii) Can be compared to solar system. (iv) Was in agreement with Thomson's model.

AAKASH SERIES-ATOMS-EXERCISE -IB
  1. Thickness of the foil of gold used in alpha-particle scattering experi...

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  2. Statement-I : In Rutherford's gold foil experiment, very few alpha-par...

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  3. In scattering experiment, find the distance of closest approach, if a ...

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  4. Rutherford experiment suggested that the size of the nucleus is about

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  5. When an electron of the hydrogen atom jumps from a higher to lower en...

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  6. According the classical theory of Rutherford's model, the path of elel...

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  7. (A) hydrogen atom consists of only one electron but its emission spect...

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  8. Assertion : It is essential that all the lines available in the emissi...

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  9. Name the material used for heating element of a room heater.

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  10. (A) for the scattering of alpha- particles at large angles, only the n...

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  11. Statement-1 : Between any two given energy levels, the number of abosr...

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  12. Balmer series lies in which region of electromagnetic spectrum

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  13. (A) bohr's postulate states that the electrons, in stationary orbits a...

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  14. (A) electrons int the atom are held due to coulomb forces. (R) the a...

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  15. In Bohr model of the hydrogen atom, let R,v and E represent the radiu...

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  16. The lines in Balmer series have their wavelengths lying between

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  17. Assertion: Magnetic force between two short magnets, when they are co-...

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  18. The energy of a photon of wavelength lambda is

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  19. (A) bohr model can not be extended to two or more electron atoms. (R...

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  20. (A) large angle of scattering of alpha particles led to the discovery ...

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