Chapter 2 – Structure of Atom
Assignment 6
Q.1. The ionization energy of He+ is 8.72 × 10–18 J atom–1. Calculate the energy of first stationary state of Li2+.
[ Ans: –19.62 × 10–18 J atom–1 ]
Q.2. What is the maximum number of emission lines when the excited electron of a H-atom in n = 6 drops to the ground state ?
[ Ans: 15 lines ]
Q.3. What transition in the hydrogen spectrum would have the same wavelength on the Balmer transition, n = 4 to n = 2 of He+ spectrum?
[ Ans: n = 2 to n = 1 ]
Q.4. Ionisation energy of hydrogen atom is 13.6 eV. What will be the ionisation energy of He+ and Li2+ ions ?
[ Ans: 54.4 eV, 122.4 eV ]
Q.5. The energy difference between two electronic states is 399.1 kJ mol–1. Calculate the wavelength and frequency of light emitted when an electron drops from a higher to a lower state. (Planck's constant, h = 3.98 × 10–13 kJ s mol–1 ).
[ Ans: 300 nm, 1 × 1015 s–1 ]
Q.6. How much energy is required to ionise a H-atom if the electron occupies n = 5 orbit ? Compare your answer with the ionization energy of H atom.
[ Ans: 8.72 × 10–20 J, 2.18 × 10–18 J ]
Q.7. What is the energy in joules required to shift the electron of the hydrogen from the first Bohr orbit to the fifth Bohr orbit and what is the wavelength of the light emitted when the electron returns to the ground state? The ground state electron energy is –2.18 × 10–11 ergs.
[ Ans: 2.09 × 10–18 J, 951 Å ]
Q.8. The energy associated with the first orbit in the hydrogen atom is –2.17 × 10–18 J atom–1. What is the energy associated with the fifth orbit?
[ Ans: – 8.68 × 10–20 J ]
Q.9. Radius of the fourth orbit in hydrogen atom is 0.85 nm. Calculate the velocity of the electron in this orbit (mass of electron = 9.1 × 10–31 kg).
[ Ans: 5.45 × 105 m s–1 ]
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