Question Pool Atoms

Atoms - SAMAGRA Question Pool & Answers | Class 12

Kerala Syllabus SAMAGRA SCERT SAMAGRA Question Pool for Class 12 Physics Atoms

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Qn 1.

Bohr proposed a new model of atom to overcome a problem of Rutherford’s atom

model.

a) Which specific problem of the Rutherford model was attempted to be solved by Bohr model?

b) What are the basic postulates of Bohr model?

c) The radius of the inner most electron orbit of a hydrogen atom is 5.3 x 10 -11 m. What are the radii of then n =2 and n=3 orbits?



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Qn 2.

The wavelength associated with a particle is called the de Broglie wavelength. From Bohr’s postulate of quantization of angular momentum arrive at an expression for the wavelength of an orbital electron. Comment on the result.



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Qn 3.

a. List out any two limitations of Bohr atom model.

b. According to de Broglie’s explanations of Bohr’s second postulate of quantization, the standing particle wave on a circular orbit for n = 4 is given by

i) 2πrn = 4/λ ii) 2π/ λ = 4rn iii) 2πrn = 4λ iv) λ / 2π = 4rn



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Qn 4.

The atomic hydrogen emits lines spectrum consisting of various series.

(a) Name the series observed first.

(b) Draw the energy level diagram of hydrogen atom.



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Qn 5.

The simple Bohr model is not applicable to He4 atoms because

a) He4 is an inert gas

b) He4 has neutrons in the nucleus

c) He4 has one more electron

d) Electrons are not subjected to central forces



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Qn 6.

The ground state energy of hydrogen atom is -13.6 eV . What are the kinetic and potential energies of the electron in this state?



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Qn 7.

A difference of 2.3 eV separates two energy levels in an atom. What is the frequency of radiation emitted when the atom makes a transition from the upper level to the lower level?



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Qn 8.

What is the shortest wavelength present in the Paschen series of spectral lines



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Qn 9.

Suppose you are given a chance to repeat the alpha-particle scattering experiment using a thin sheet of solid hydrogen in place of the gold foil. (Hydrogen is a solid at temperatures below 14 K) What results do you expect?



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Qn 10.

The positively charged part of the atom possesses most of the mass in .............(Rutherford’s model/both the models).



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Qn 11.

An atom has a nearly continuous mass distribution in a .........but has a highly non-uniform mass distribution in ............ (Thomson’s model/Rutherford’s model)



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Qn 12.

A classical atom based on ..........is doomed to collapse. (Thomson’s model/Rutherford’s model.)



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Qn 13.

In the ground state of ........... electrons are in stable equilibrium, while in.............. electrons always experience a net force. (Thomson’s model/Rutherford’s model.)



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Qn 14.

The size of the atom in Thomson’s model is ............ the atomic size in Ruther ford’s model. (much greater than/not different from/much less than)



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Qn 15.

Louis de Broglie argued that electron in circular orbit as proposed by Bohr, must be seen as a Particle wave.

a)From Bohr’s postulate of angular quantization momentum, arrive at an expression for wave length of an orbital electron?

b)Comment on the above result.



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Qn 16.

Bohr combined classical and early quantum concept and gave his theory in form of three postulates.

a)State three postulates of Bohr Model of atom?

b)The total energy of an electron in ground state of an hydrogen atom is - 13.6 eV. What is the significance of negative sign?

             c)The radius of inner most electron orbit of hydrogen atom is 5.3x10-11 m. What are the radii of n=2 and n=3 orbits?



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Qn 17.

Study of emission line spectra of a material serve as a fingerprint for identification of the gas.

a)Name different series of lines observed in hydrogen spectrum

b)Draw energy level diagram of hydrogen atom?

c)Write down the Balmer formula for wavelengthof Hαline. (1)

d)Given Rydberg constant as 1. 097x107 m-1. Find the longest and shortest wavelength limit of Balmer Series.



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Qn 18.

Draw the energy level diagram of hydrogen spectrum



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Qn 19.

In Rutherford’s α particles scattering experiment ,he used particles of energy 5.5 MeV and gold foil of thickness as small as 2.1x10-10m

a)What will be the angle of scattering when impact parameter is zero

b)How does the angle of scattering change with impact parameter

c)Why the size of gold foil is made extremely small

d)Can you conduct the experiment with aluminium foil



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Qn 20.

Louis de Broglie argued that electron in circular orbit as proposed by Bohr, must be seen as a

Particle wave.

a) From Bohr’s postulate of angular quantization momentum, arrive at an expression for

wave length of an orbital electron?

b) Comment on the above result.



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Qn 21.

Study of emission line spectra of a material serve as a fingerprint for identification of the

gas.

(a) Name different series of lines observed in hydrogen spectrum

(b) Draw energy level diagram of hydrogen atom?

(c) Write down the Balmer formula for wave length of Hα line.

(d) Given Rydberg constant as 1. 097x107 m-1. Find the longest and shortest wavelength

limit of Balmer Series.



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Qn 22.

In Geiger-Marsden Scattering experiment alpha particles of 5.5 MeV is allowed to fall on a

thin gold foil of thickness 2.1x10-7m.

(a).Draw Schematic diagram of above experimental arrangement.

b)In the above graph nearly 107 particles were detected when scattering angle is Zero.

What you understand by it?

(c) Why gold foil is used in this experiment?

(d) Does there exist any relation between impact parameter and scattering angle? If yes

explain your answer?



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Qn 23.

A 12.5 eV electron beam is used to bombard gaseous hydrogen at room temperature. What series of wavelengths will be emitted?



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Qn 24.

 

The radius of the innermost electron orbit of a hydrogen atom is  . What are the radii of the n = 2 and n =3 orbits?



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