ATOMS
Questions for Practice
Choose and write the correct option in the following questions
1..The ratio of kinetic energy to the total energy of an electron In a Bohr orbit of the hydroge
atom, is
(a) 1:2
(b) 2:1
(c) 1:-1
(d) 1:1
2. The ratio of maximum frequency and minimum frequency of light emitted in Balmer
Series of hydrogen spectrum, in Bohr's model is
a)11/9
(b)9/5
(c) 11/7
(d)16/7
4. In which region of the electromagnetic spectrum does the Lyman series of hydrogen lie?
(a) Ultraviolet
(b) Infra-red
(c) Visible
(d) X-ray
5. What is the relation between orbit radius 'r and orbit number 'n' of electron in an atom
according to Bohr's theory?
(a) rαn-1
(b) rαn
(c) rαn-2
(d) rαn2
6.Choose the correct answer out of the following choices.
Assertion (A) : Hydrogen atom consists of only one electron but its emission spectrum has many lines.
Reason : Only Lyman series is found in the absorption spectrum of hydrogen atom whereas in the
emission spectrum, all the series are found.
7. When electron in hydrogen atom jumps from energy state n, =4 to n, =3, 2, 1, identify the spectral
series to which the emission lines belong.
8.The energy of electron in nth orbit of H-atom is E, =-13.6/n2
What is the energy required for transition from ground state to first excited state?
9.Define ionisation energy. What is its value for a hydrogen atom?
10.hydrogen atom initially in the ground state absorbs a photon which excites it to the
n=4 level. Estimate the frequency of the photon.
11. The ground state energy of hydrogen atom is – 13.6 eV. If an electron makes a transition from an
energy level - 0.85 eV to -3.4 eV, calculate the wavelength of the spectral line emitted.
12. The ground state energy of hydrogen atom is -13.6 eV. What is the kinetic and potential energies of
the electron in the ground and second excited state?
13. The radius of innermost orbit of a hydrogen atom is 5.3X 10-11m. What are the radii of n=2 orbits?
14. In accordance with Bohr's model, find the quantum number, that characterizes the earth's revolution
around the sun in an orbit of radius 1.5 x 10" m with orbital speed3 x 104m/s. (Mass ofearth = 6.0 x 1024
kg)
15. Write two important limitations of Rutherford nuclear model of the atom.
16. Find out the wavelength of the electron orbiting in the ground state of hydrogen atom.
17. A hydrogen atom in the ground state is excited by an electron beam of 12.5 eV energy. Find
maximum number of lines emitted by the atom from its excited state.
18. State Bohr's postulate to explain stable orbits in a hydrogen atom. Prove that the speed with which
the electron revolves in nth orbit is proportional to (1/n).
19. The short wavelength limit for the Lyman series of the hydrogen spectrum is 913.4 Å. Calculate the
short wavelength limit for Balmer series of the hydrogen spectrum.
