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Chap 12 Physics Top 10

The document provides 9 important questions from Chapter 12 on atoms for board exams. The questions cover Rutherford's atomic model, Bohr's model of the hydrogen atom, Geiger-Marsden experiment, nuclear density, energy levels, line spectra, and properties derived from Bohr's postulates including orbital radii and electron energy. Students are advised to study these concepts in depth as they make up 6 marks of the board exam weightage for Chapters 12 and 13.

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Gaurav Sinha
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337 views2 pages

Chap 12 Physics Top 10

The document provides 9 important questions from Chapter 12 on atoms for board exams. The questions cover Rutherford's atomic model, Bohr's model of the hydrogen atom, Geiger-Marsden experiment, nuclear density, energy levels, line spectra, and properties derived from Bohr's postulates including orbital radii and electron energy. Students are advised to study these concepts in depth as they make up 6 marks of the board exam weightage for Chapters 12 and 13.

Uploaded by

Gaurav Sinha
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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ARVIND ACADEMY YouTube Channel Click the link to see the video

https://youtu.be/1FD0xTvSMNg

Chap 12 : Atoms
Important Questions for Board Exams
Board Weightage 6 Marks (Chap 12+13)

1. Write basic assumption of Rutherford’s atomic model & also exapli the
drawbacks of Rutherford’s model.

2. Explain Bohr’s theory of hydrogen atom in the form of three postulates &
also point out the limitations of Bohr’s model.

3. What do you mean by distance of closest approach & also write the
formula with proper symbols explanations.

4. In the Study of Geiger-Marsden experiment on scattering of alpha particles


by a thin foil of gold, draw the trajectory of alpha particles in the coulomb
field of target nucleus. Explain briefly how one gets the information on the
size of the nucleus from this study.

𝟏
From the relation 𝑹 = 𝑹𝟎 𝑨 ⁄𝟑 , where R0 is constant & A is the mass
number of the nucleus, show that nuclear matter density is independent
of A.

5. Using the postulates of Bohr’s model of hydrogen atom, obtain an


expression for the frequency of radiation emitted when the atom makes a
transition from the higher energy state with quantum number ni to the
lower energy state with quantum number nf. Where nf is smaller than ni.

6. Using Bohr’s postulates, obtain the expression for the total energy of the
electron in the stationary states of the hydrogen atom. Hence draw the
energy level diagram showing how the line spectra corresponding to
Balmer series occur due to transition between energy levels.

7. The value of ground state energy of hydrogen atom is -13.6 eV.


(i) Find the energy required to move an electron from the ground state
to the first excited state of the atom. Ans 10.2 eV
(ii) Determine (a) kinetic energy and (b) orbital radius in the first
excited state of the atom. (Given, the value of the Bohr’s radius =
0.53 Å. Ans (a) 3.4 eV (b) 2.12 Å

8. The electron in a given Bohr orbit has a total energy of -1.5 eV. Calculate
its
(i) Kinetic Energy
(ii) Potential energy
ARVIND ACADEMY YouTube Channel Click the link to see the video
https://youtu.be/1FD0xTvSMNg

(iii) Wavelength of radiation emitted, when this electron makes a


transition to the ground state. [Given, energy in the ground state
= -13.6 eV and Rydberg’s constant =1.09 x 107 m-1 ] Ans (i) 1.5 eV
(ii) -3 eV (iii) 𝝀 = 𝟏𝟎𝟐𝟓 Å

9. Using postulates of Bohr’s theory of hydrogen atom, show that


(i) Radii of orbits increases as n2 and
𝟏
(ii) The total energy of electron increases as 𝟐 , where n is the
𝒏
principal quantum number of the atom.

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