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# what to study in atoms and nuclei chapter for AISSCE?

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What to study in atoms and nuclei chapter for AISSCE?

As per CBSE Syllabus the contents are

### Chapter–12: Atoms

Alpha-particle scattering experiment; Rutherford’s model of atom; Bohr model, energy levels, hydrogen spectrum.

### Chapter–13: Nuclei

Composition and size of nucleus, Radioactivity, alpha, beta and gamma particles/rays and their properties; radioactive decay law.
Mass-energy relation, mass defect; binding energy per nucleon and its variation with mass number; nuclear fission, nuclear fusion.

Though all portions are to be learnt, the topics given in bold above needs more attention.

Have a look at the following questions which are frequently asked from the unit. These questions are collected from previous question papers

1. Why is it found experimentally difficult to detect neutrinos in nuclear
beta -decay ?
2. Using Rutherford model of the atom, derive the expression for the total energy of the electron in hydrogen atom. What is the significance of total negative energy possessed by the electron ?
3. Using Bohr’s postulates of the atomic model, derive the expression for radius of nth electron orbit. Hence obtain the expression for Bohr’s radius.
4. The figure shows energy level diagram of hydrogen atom.
(a) Find out the transition which results in the emission of a photon of wavelength
496 nm.
n = 4
n = 3
n = 2
n = 1
(b) Which transition corresponds to the emission of radiation of maximum
5. (a) Complete the following nuclear reactions :
(i) 208Po84 –>  204Pb82 + …
(ii) 32P 15 –> 32S16 + …
(b) Write the basic process involved in nuclei responsible for (i) beta– and (ii) beta+ decay.
(c) Why is it found experimentally difficult to detect neutrinos ?
6. (a) Write the relation for binding energy (BE) (in MeV) of a nucleus of
mass M, atomic number (Z) and mass number (A) in terms of the
masses of its constituents — neutrons and protons.
(b) Draw a plot of BE/A versus mass number A for 2 <= A <= 170. Use
this graph to explain the release of energy in the process of nuclear
fusion of two light nuclei.

ALSO PRACTICE

1. Describe Rutherford’s alpha scattering experiment with neat labelled diagram and write the conclusions drawn from the result of experiment.
2. Derive an expression for the distance of closest approach in Rutherford’s alpha scattering experiment.
3. State postulates of Bohr atom model.
4. What are the drawbacks of Rutherford’s model of atom?
5. Describe the formula for spectral series of hydrogen atom and draw diagram showing the transitions resulting in various spectral series of hydrogen.
6. State the properties of nuclear force.
7. Draw graph showing the variation of Binding Energy per nucleon and explain the release of energy during nuclear fission and fusion using the graph.
8. Show that the nuclear density is independent of mass number.
10. Define half-life of a radioactive element and derive an expression for it in terms of decay constant.

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