10 Question-answer on models of atoms
1. In an atom, the two electrons move round the nucleus in circular orbits of radii R and 4R. The ratio of the times taken by them to complete one revolution is:
(a) ¼
(b) 4/1
(c) 8/1
(d) 1/8
Ans: (d)
2. The ratio of the energies of the hydrogen atom in its first to second excited states is:
(a) ¼
(b) 4/9
(c) 9/4
(d) 4.
Ans: (c)
3. For the principle quantum number n=4, the total number of different possible values of the azimuthal quantum number l, is
(a) 2
(b) 8
(c) 4
(d) 3.
Ans: (c)
4. Consider the spectral line resulting from the transition n=2 to n=1 in the atoms and the ions given below. The shortest wavelength is produced by:
(a) Hydrogen atom
(b) Deuterium atom
(c) Singly lonised helium
(d) Doubly jonised lithium.
Ans: ( d)
5. For the azimuthal quantum number l=3, the total number of different possible values of the magnetic azimuthal quantum number, m1, is:
(a) 3
(b) 4
(c) 5
(d) 7
Ans: (d)
6. With increasing quantum number, the energy difference between adjacent energy levels in atoms:
(a) Decreases
(b) Increases
(c) Remains constant
(d) Decreases for low z and increases for high z.
Ans: (a)
7. The series limit wavelength of the Lyman series for the hydrogen atom is given by
(a) 1/R
(b) 4/R
(c) 9/R
(d) 16/R
Ans: (a)
8. The valence electron in an alkali metal is:
(a) An f electron
(b) A p electron
(c) An s electron
(d) A d electron
Ans: (c)
9. The ionization energy of hydrogen atom is 13.6 eV. Following Bohr’s theory, the energy corresponding to a transition between 3rd and 4th orbit is:
(a) 3.40 eV
(b) 1.51 eV
(c) 0.85 eV
(d) 0.66 eV
Ans: ( d)
10. A hydrogen atom in the ground state is excited by radiations of wavelength 975 A. the energy state to which the atom is excited is:
(a) 1
(b) 2
(c) 3
(d) 4
Ans: ( d)