Class 9 Atoms and Molecules MCQ. We covered all the Class 9 Atoms and Molecules MCQ in this post for free so that you can practice well for the exam.
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MCQ on Atoms and Molecules for NEET Students
According to Rutherford’s atomic model, the electrons inside the atom are ………..
(A) centralized
(B) deviated
(C) not stationary
(D) stationary
Option c – not stationary
In a hydrogen atom, if the difference in the energy of the electron in n = 3 and n = 4 orbits is E, then the ionization energy of the hydrogen atom is
(A) 13.21E
(B) 7.28E
(C) 20.57E
(D) 3.33E
Option c – 20.57E
The ratio of minimum to maximum wavelength in the Balmer series is
(A) 5 : 9
(B) 5 : 36
(C) 1 : 4
(D) 3 : 4
Option a – 5 : 9
Which of the following statements about the Bohr model of the hydrogen atom is TRUE?
(A) The acceleration of the electron in the n = 2 orbit is more than that in the n = 1 orbit.
(B) The angular momentum of an electron in the n = 2 orbit is more than that in the n = 1 orbit.
(C) The kinetic energy of an electron in the n = 2 orbit is more than that in the n = 1 orbit.
(D) The potential energy of an electron in the n = 2 orbit is less than that in the n = 1 orbit.
Option b – The angular momentum of an electron in the n = 2 orbit is more than that in the n = 1 orbit.
As an electron makes a transition from a higher orbit to the lower orbit of a hydrogen-like atom/ion
(A) kinetic energy, potential energy, and total energy decrease.
(B) its kinetic energy increases but potential energy and total energy decrease.
(C) kinetic energy and total energy decrease but potential energy increases.
(D) kinetic energy decreases, potential energy increases but the total energy remains the same.
Option b – its kinetic energy increases but potential energy and total energy decrease.
Which of the following is correct for the number of spectral lines observed in going from the Lyman series to the Pfund series when an electron jumps from the 10th orbit?
(A) Increases.
(B) Decreases.
(C) Unchanged.
(D) May decrease or increase.
Option b – Decreases.
The concept of stationary orbits was proposed by ………
(A) Niels Bohr
(B) Rutherford
(C) J.J. Thomson
(D) Balmer
Option a – Niels Bohr
If an electron jumps from the 3rd orbit to the 1st orbit, then it will
(A) absorb energy.
(B) release energy.
(C) possess the same energy.
(D) lose -13.6 eV energy.
Option b – release energy.
The ionization energy of hydrogen is 13.6 eV. The energy of the photon released when an electron jumps from the second excited state to the ground state of a hydrogen atom is
(A) 3.4 eV
(B) 1.51 eV
(C) 12.09 eV
(D) 10.2 eV
Option c – 12.09 eV
With the decrease in principal quantum number, the energy difference between the two successive energy levels
(A) increases.
(B) decreases.
(C) remains constant.
(D) sometimes increases and sometimes decreases.
Option a – increases.
The area of the electron orbit for the ground state of a hydrogen atom is A. What will be the area of the electron orbit corresponding to the third excited state?
(A) 27A
(B) 64A
(C) 81A
(D) 256A
Option d – 256A
Assertion: The density of the nuclei of all the atoms are same. Reason: The density of the nucleus depends on the mass number.
(A) The assertion is True, Reason is True; Reason is a correct explanation for Assertion.
(B) The assertion is True, and Reason is True; Reason is not a correct explanation for Assertion.
(C) The assertion is True, Reason is False.
(D) The assertion is False, Reason is False.
Option c – The assertion is True, Reason is False.
The minimum energy required to take out only an electron from the ground state of He is one
(A) 13.6 eV
(B) 54.4 eV
(C) 27.2 eV
(D) 6.8 eV
Option b – 54.4 eV
The required to knock electron energy from the third orbit in eV will be
(A) 1.51
(B) 0.38
(C) 13.6
(D) 3.4
Option a – 1.51
The force acting between proton and proton inside the nucleus is ………. force.
(A) Coulomb
(B) Nuclear
(C) Coulomb and nuclear
(D) Gravitational
Option c – Coulomb and nuclear
The ionization potential of a hydrogen atom is 13.6 eV. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.75 eV. The spectral lines emitted by hydrogen atoms according to Bohr’s theory will be
(A) Six
(B) Two
(C) Three
(D) Four
Option a – Six
In which of the following atoms and molecules, will the spectral line of minimum wavelength be produced for the transition from n = 2 to n = 1?
(A) Deuterium atom.
(B) Hydrogen atom.
(C) Di-ionized lithium.
(D) Uni-ionized helium.
Option c – Di-ionized lithium.
The ratio of the velocity of the electron in the first orbit to that in the third orbit is
(A) 27 : 1
(B) 9 : 1
(C) 3 : 1
(D) 1 : 3
Option c – 3 : 1
As per the Bohr model, the minimum energy (in eV) required to remove an electron from the ground state of a doubly ionized Li atom (Z = 3) is
(A) 1.51
(B) 13.6
(C) 40.8
(D) 122.4
Option d – 122.4
The ratio of maximum to minimum wavelength in the Balmer series is
(A) 5 : 9
(B) 36 : 9
(C) 9 : 5
(D) 3 : 4
Option c – 9 : 5
Which of the following transitions has a higher frequency?
(A) 4→3
(B) 3 →1
(C) 4→2
(D) 3→2
Option b – 3 → 1
What would be the possible number of elements, if elements with principal quantum number n > 4 did not exist in nature?
(A) 60
(B) 32
(C) 28
(D) 110
Option a – 60
The size of the nucleus in an atom is almost equal to
(A) 1 weber
(B) 1 tesla
(C) 1 fermi
(D) 1 henry
Option c – 1 fermi
The minimum excitation potential of Bohr’s fin orbit in a hydrogen atom is ( Class 9 Atoms and Molecules MCQ )
(A) 13.6 V
(B) 3.4 V
(C) 10.2 V
(D) 10.2 eV
Option c – 10.2 V
A monochromatic beam of light is absorbed by a collector of ground-state hydrogen atom in such a way that six different wavelengths are observed when hydrogen relaxes back to the ground state The wavelength of the incident beam is
(A) 97 nm
(B) 91 nm
(C) 68 nm
(D) 85 nm
Option a – 97 nm
In the Bohr model of the hydrogen atom, the highest orbit corresponds to
(A) infinite energy.
(B) the maximum energy.
(C) the minimum energy.
(D) zero energy.
Option b – the maximum energy.
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