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ATOMS AND NUCLEI

Question bank (Schrödinger Group)

ONE MARK QUESTIONS

1.

What will be the ratio of radii of two nuclei of mass numbers A1 and A2?

2.

What is Bohr quantization condition for the angular momentum of electron in the second orbit?

3.

The sequence is represented as if the mass numbers and atomic numbers of D2 are 176 and 71 respectively, what is the mass number and atomic number of D.

4.

The wavelength of some of the spectral lines obtained in hydrogen spectrum are 9546 A, 6463 A, 1216 A. which one of these wavelengths belongs to Lymann series.

5.

Why do α particles have high ionizing power?

6.

What happens to the neutron to protn ratio after the emission of alpha particles?

7.

Define impact parameter.

8.

What is the ratio of nuclear densities of two nuclei having mass number 1:4?

TWO MARKS QUESTIONS

9.

Assuming the nuclei to be spherical in shape how does the surface area of nucleus of mass number A1 vary with that of nucleus of mass number A2?

10.

Radioactive isotope of silver has half-life of 20 minutes. What fraction of the original mass would remain after one hour?

11.

Group the following four nuclides into two pairs of isotones and isobars.

12.

Draw a graph showing the variation of potential energy between the pair of nucleons as the function of their separation. Indicate the regions in which the nuclear force is attractive and repulsive.

13.

Calculate the radius of the smallest orbit of hydrogen atom.

14.

Calculate the frequency of the photon which can excite an electron to -3.4 eV from -13.6 eV.

15.

You are given two nuclei explain giving reasons as to which one of the nuclei is likely to be more stable.

16.

Show that the speed of the electron in the second orbit of hydrogen like atom He+ is equal to speed of an electron in the hydrogen atom.

17.

What are the limitations of Bohr atomic model?

18.

The energy levels of an element X are shown in the figure. A hoton of wavelength 620 nm is emitted and this corresponds to which of the transition A, B, C, D or E?

3 MARKS QUESTIONS

19.

Calculate the speed of electron revolving around the nucleus of a hydrogen atom in order that it may not be pulled into the nucleus by electrostatic attraction.

20.

What is the distance of closest approach and derive an expression for the same?

21.

Draw a labeled diagram of Geiger – Marsden experiment on th scattering of α particles. How is the size of the nucleus estimated based on the experiment?

22.

Derive an expression for the potential and kinetic energy of an electron in any orbit of a hydrogen atom. How does the potential energy change with increasing n?

23.

Show that Bohr’s second postulate “The electron revolves around the nucleus only in certain fixed orbits without radiating energy” can be explained on the basis of de – Broglie hypothesis of wave nature of electron.

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