| (a) Angular momentum must be an integral multiple of h/2π or L = nh/2π or L = mvr = nh/2π (b) See Figure |
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| Previous Year Questions of March Examinations from 2010 to 2020 |
| Chapter Name: ATOMS |
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The total energy of an electron in the ground state of a hydrogen atom is -13.6eV. a) What do you mean by ground state of a hydrogen atom? b) The excitation energy required to raise the electron in the first excited state of hydrogen atom is .............eV. |
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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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Niels Bohr explained hydrogen spectrum based on quantum ideas. a) Draw the energy level diagram of hydrogen atom. b) Name the different series of lines observed in hydrogen spectrum. c) Show the transitions between energy levels producing the different series. |
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Rutherford atom model is based on the classical concept that electrons are revolving around a central positive nucleus a) Mention the drawback of Rutherford atom model and how it is rectified in Bohr’s atom model? b) From Bohr’s theory obtain the de Broglie wavelength of an electronorbiting around the nucleus c) Give the statement of Heisenberg’s uncertainty principle and express it mathematically |
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When a vapour is exited at low pressure by passing an electric current through it, a spectrum is obtained a) Draw a spectral series of emission lines in hydrogen b) Name the different series of hydrogen atom c) In which region Lyman series is located |
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(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 a) 2πrn = 4/λ b) 2π / λ = 4rn c) 2πrn = 4 λ d) λ/2π = 4rn |
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(a) Unit of wave number is (i) Hz (ii) eV (iii) m (iv) m-1 (b) Energy of ground state of hydrogen atom is 13.6 eV. What is its ionisation potential? |
| How many electrons, protons and neutrons are there in 16g of 8O16 ? |
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(a) Name difterent series of lines observed in hydrogen spectrum. (b) Draw energy level diagram of hydrogen atom. |
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Niels Bohr made certain modification in Rutherford"s model by adding the ideas of hypothesis. (a) State Bohr"s second postulate of quantisation of angular momentum. (b) Derive an expression for the radius and energy of the electron in the nth orbit of hydrogen atom. |
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The size of the atom in Thomson"s model is _____ the atomic size in Rutherford"s model. (a) much greater than (b) not different from (c) much less than |
| The atomic line spectra of hydrogen atom is shown in figure. Write the names of the series A, B and C. |
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