Q. If 13.6 eV energy is required to ionise the hydrogen atom, then energy required to remove an electron from n = 2 is
✅ Correct Answer: (C)
3.4 eV
Atoms MCQs with answers
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Q. In Bohr’s model of an atom which of the following is an integral multiple of h2π?
✅ Correct Answer: (D)
Angular momentum
Q. In Bohr’s model, the atomic radius of the first orbit is rQ. Then, the radius of the third orbit is
✅ Correct Answer: (C)
9r0
Q. The longest wavelength in Balmer series of hydrogen spectrum will be
✅ Correct Answer: (A)
6557 Å
Q. In terms of Rydberg constant R, the wave number of the first Balmer line is
✅ Correct Answer: (C)
5R36
Q. The ionisation energy of hydrogen atom is 13.6 eV. Following Bohr’s theory the energy corresponding to a transition between 3rd and 4th orbits is
✅ Correct Answer: (D)
0.66 eV
Q. On moving up in the energy states of a H-like atom, the energy difference between two consecutive energy states
✅ Correct Answer: (A)
decreases
Q. The Bohr model for the spectra of a H-atom
✅ Correct Answer: (B)
will not be applicable as it is for a He- atom.
Q. Consider aiming a beam of free electrons towards free protons. When they scatter, an electron and a proton cannot combine to produce a H-atom,
✅ Correct Answer: (B)
without simultaneously releasing energy in the from of radiation.
Q. The binding energy of a H-atom, considering an electron moving around a fixed nuclei (proton), is
B=−me48n2ε20h2. (m = electron mass)
If one decides to work in a frame of reference where the electron is at rest, the proton would be moving arround it. By similar arguments, the binding energy would be
B=−Me48n2ε20h2(M= proton mass)
This last expression is not correct because
B=−me48n2ε20h2. (m = electron mass)
If one decides to work in a frame of reference where the electron is at rest, the proton would be moving arround it. By similar arguments, the binding energy would be
B=−Me48n2ε20h2(M= proton mass)
This last expression is not correct because
✅ Correct Answer: (C)
the frame in which the electron is at rest is not inertial.
Q. For ionising an exicited hydrogan atom, the energy required (in eV) will be
✅ Correct Answer: (D)
3.4 or less
Q. The Bohr model of an atom
✅ Correct Answer: (A)
assumes that the angular momentum of electrons is quantised
Q. Let En=−18ε20me4n2h2 be the energy of the nth level of H-atom. If all the H-atoms are in the ground state and radiation of frequency (E2 – E1)/h falls on it,
✅ Correct Answer: (D)
all atoms will make a transition to the n = 3 state.
Q. The Balmer series for the H-atom can be observed
✅ Correct Answer: (B)
if we measure the frequencies of light emitted due to transitions between excited states and the first excited state.
Q. An ionised H-molecule consists of an electron and two protons. The protons are separated by a small distance of the order of angstrom. In the ground state,
✅ Correct Answer: (C)
the electrons, orbit would go around the protons.
Q. A set of atoms in an excited state decays
✅ Correct Answer: (A)
in general to any of the states with lower energy.
Q. Two H atoms in the ground state collide inelastically. The maximum amount by which their combined kinetic energy is reduced is
✅ Correct Answer: (A)
10.20 eV
Q. 02 molecule consists of two oxygen atoms. In the molecule, nuclear force between the nuclei of the two atoms
✅ Correct Answer: (A)
is not important because nuclear forces are short-ranged.
Q. For the ground state, the electron in the H-atom has an angular momentum = h, according to the simple Bohr model. Angular momentum is a vector and hence there will be infinitely many orbits with the vector pointing in all possible directions. In actuality, this is not true,
✅ Correct Answer: (A)
because Bohr model gives incorrect values of angular momentum.
Q. The simple Bohr model cannot be directly applied to calculate the energy levels of an atom with many electrons. This is because
✅ Correct Answer: (D)
of the electrons not being subject to a central force.
Q. Taking the Bohr radius as a0 = 53 pm, the radius of Li++ ion in its ground state, on the basis of Bohr’s model, will be about
✅ Correct Answer: (C)
18 pm
Q. The spectral lines in the Brackett series arise due to transition of electron in hydrogen atom from higher orbits to the orbit with
✅ Correct Answer: (D)
n = 4
Q. The transition of electron from n = 4, 5, 6, ………. to n = 3 corresponds to
✅ Correct Answer: (C)
Paschen series
Q. As per Bohr model, the minimum energy (in eV) required to remove an electron from the ground state of double ionized Li atom (Z = 3) is
✅ Correct Answer: (D)
122.4 eV
Q. Which of the following spectral series in hydrogen atom gives spectral line of 4860 A?
✅ Correct Answer: (B)
Balmer
Q. In Geiger-Marsden scattering experiment, the trajectory traced by an a-particle depends on
✅ Correct Answer: (C)
impact parameter
Q. In the Geiger-Marsden scattering experiment the number of scattered particles detected are maximum and minimum at the scattering angles respectively at
✅ Correct Answer: (A)
0° and 180°
Q. In the Geiger-Marsden scattering experiment, is case of head-on collision the impact parameter should be
✅ Correct Answer: (A)
maximum
Q. Rutherford’s experiments suggested that the size of the nucleus is about
✅ Correct Answer: (C)
10-15 m to 10-14 m
Q. Which of the following spectral series falls within the visible range of electromagnetic radiation?
✅ Correct Answer: (B)
Balmer series
Q. The hydrogen atom can give spectral lines in the Lyman, Balmer and Paschen series. Which of the following statement is correct?
✅ Correct Answer: (B)
Balmer series is in the visible region.
Q. The transition from the state n = 5 to n = 1 in a hydrogen atom results in UV radiation. Infrared radiation will be obtained in the transition
✅ Correct Answer: (C)
4 → 3
Q. The diagram shows the energy levels for an electron in a certain atom. Which transition shown represents the emission of a photon with the most energy?
✅ Correct Answer: (C)
III
Q. If tt is the orbit number of the electron in a hydrogen atom, the correct statement among the following is
✅ Correct Answer: (A)
electron energy increases as n increases.
Q. The Bohr model of atoms
✅ Correct Answer: (A)
assumes that the angular momentum of elec-trons is quantized.
Q. Which of the following postulates of the Bohr model led to the quantization of energy of the hydrogen atom?
✅ Correct Answer: (B)
The angular momentum of the electron can only be an integral multiple of h/2π.
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