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Q1. A radioactive uncleus undergoes a series of decay according to the scheme If the mass number and atoms number of A are 180 and 72 respectively, what are there number for A₄?

Solution

Q2. The ground state energy of hydrogen atom is -13.6eV (i) What is the kinetic energy of an electron in the second excited state ? (ii) If the electron jumps to the ground state from the second excited state, calculate the wavelength of the spectral line emitted.   OR  

Solution

OR

Q3. Give the mass number and atomic number of elements on the right hand side of the decay process.

Solution

The complete equation representing mass number and atomic number is given below For Polonium Z=84, A=216 For Helium Z=2, A=4

Q4.   Complete the following nuclear reactions (a) 4B_e⁹ + ₁H¹ →3L_i⁶ + ................ (b) 5B¹⁰ + →  + ..............  

Solution

(a) 4B_e⁹ + 1H¹ →3L_i⁶ + (b) 5B¹⁰ + → + on¹

Q5. The isotopes ₈O¹⁶ has 8 protons, 8 neutrons and 8 electrons, while ₄Be⁸ has 4 protons, 4 neutrons and 4 electrons. Yet the ratio of their atomic masses is not exactly 2. Why?

Solution

The ratio of mass of ₈O¹⁶ and mass of ₄Be⁸ is not exactly two because of difference in the mass defect/binding energy of the atomic nuclei of the two elements.

Q6. A radioactive sample contains 2.2 mg of pure which has half life period of 1224 seconds. Calculate (i) the number of atoms present initially. (ii) the activity when 5μg of the sample will be left.

Solution

  (i) By definition 11g of carbon contains N_A = 6.023 x 10²³ atoms number of atoms in 2.2 mg = 2.2 x 10^-3g of will be                                         = (ii) Activity A = λN Half life T_1/2 = Activity A = Where N = Number of atoms in 5μg (= 5 x 10^-6g) which is equal to  

Q7. What will be the ratio of radii of two nuclei of mass number A₁ and A₂?

Solution

Q8. The half life period of a radioactive substance is 30 days. What is the time for ¾ th of its original mass to disintegrate?

Solution

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