MCQs on Class 11 Chemistry Chapter 2 Structure of Atom

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Questions
1 Chlorine exists in two isotopic forms, Cl-37 and Cl-35 but its atomic mass is 35.5. This indicates the ratio of Cl-37 and Cl-35 is approximately
A 1:2
B 1:1
C 1:3
D 3:1

Answer:1:3
2 Total number of orbitals associated with third shell will be __________.
A 2
B 4
C 9
D 3

Answer:9
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3 Two atoms are said to be isobars if.
A they have same atomic number but different mass number.
B they have same number of electrons but different number of neutrons.
C they have same number of neutrons but different number of electrons.
D sum of the number of protons and neutrons is same but the number of protons is different.

Answer:sum of the number of protons and neutrons is same but the number of protons is different.
4 Which of the following properties of atom could be explained correctly by Thomson Model of atom?
A Overall neutrality of atom.
B Spectra of hydrogen atom.
C Position of electrons, protons and neutrons in atom.
D Stability of atom.

Answer:Overall neutrality of atom.
5 Which of the following statements about the electron is incorrect?
A It is a negatively charged particle.
B The mass of electron is equal to the mass of neutron.
C It is a basic constituent of all atoms.
D It is a constituent of cathode rays.

Answer:The mass of electron is equal to the mass of neutron.
6 Which of the following statement is not correct about the characteristics of cathode rays?
A They start from the cathode and move towards the anode.
B They travel in straight line in the absence of an external electrical or magnetic field.
C Characteristics of cathode rays do not depend upon the material of electrodes in cathode ray tube.
D Characteristics of cathode rays depend upon the nature of gas present in the cathode ray tube.

Answer:Characteristics of cathode rays depend upon the nature of gas present in the cathode ray tube.
7 The probability density plots of 1s and 2s orbitals are given in Fig

Structure of Atom

The density of dots in a region represents the probability density of finding electrons in the region.

On the basis of above diagram which of the following statements is incorrect?

A 1s and 2s orbitals are spherical in shape.
B The probability of finding the electron is maximum near the nucleus.
C The probability of finding the electron at a given distance is equal in all directions.
D The probability density of electrons for 2s orbital decreases uniformly as distance from the nucleus increases.

Answer:The probability density of electrons for 2s orbital decreases uniformly as distance from the nucleus increases.
8 Which of the following options does not represent ground state electronic configuration of an atom?
A 1s2 2s2 2p6 3s2 3p6 3d8 4s2
B 1s2 2s2 2p6 3s2 3p6 3d9 4s2
C 1s2 2s2 2p6 3s2 3p6 3d10 4s1
D 1s2 2s2 2p6 3s2 3p6 3d5 4s1

Answer:1s2 2s2 2p6 3s2 3p6 3d9 4s2
9 Which of the following conclusions could not be derived from Rutherford’s α -particle scattering experiment?
A Most of the space in the atom is empty.
B The radius of the atom is about 10–10 m while that of nucleus is 10–15 m.
C Electrons move in a circular path of fixed energy called orbits.
D Electrons and the nucleus are held together by electrostatic forces of attraction.

Answer:Electrons move in a circular path of fixed energy called orbits.
10 In which of the following pairs, the ions are iso-electronic?
A Na+, Mg2+
B Al3+, O–
C Na+, O2-
D N3–, Cl–

Answer:C, D
11 Maximum number of electrons in a subshell with l = 3 and n = 4 is
A 10
B 12
C 14
D 16

Answer:14
12 The correct set of four quantum numbers for the valence electron of rubidium atom (Z = 37) is
A 5, 0, 0, + 1/2
B 5, 1, 0, + 1/2
C 5, 1, 1, + 1/2
D 6, 0, 0, + 1/2

Answer:5, 0, 0, + 1/2
13 Identify the wrong statement in the following
A Atomic radius of the elements increases as one moves down the first group of the periodic table
B Atomic radius of the elements decreases as one moves across from left to right in the 2nd period of the
C Amongst isoelectronic species, smaller the positive charge on the cation, smaller is the ionic radius
D Amongst isoelectronic species, greater the negative charge on the anion, larger is the ionic radius

Answer:Amongst isoelectronic species, smaller the positive charge on the cation, smaller is the ionic radius
14 A gas absorbs a photon of 355 nm and emits at two wavelengths. If one of the emissions is at 680 nm, the other is at: [AIEEE 2011]
A 518 nm
B 1035 nm
C 325 nm
D 743 nm

Answer:743 nm
15 The energy of an electron in first Bohr orbit of H-atom is –13.6 eV. The possible energy value of electron in the excited state of Li2+ is [West Bengal JEE 2011]
A – 122.4 eV
B 30.6 eV
C – 30.6 eV
D 13.6 eV

Answer: – 30.6 eV
16 The electronic transitions from n = 2 to n = 1 will produce shortest wavelength in (where n = principal quantum state) [West Bengal JEE 2011]
A Li+2
B He+
C H
D H+

Answer:Li+2
17 The energy required to break one mole of Cl – Cl bonds in Cl2 is 242 kJ mol–1. The longest wavelength of light capable of breaking a single Cl – Cl bond is

(c = 3×108 ms–1 and NA = 6.02×1023 mol–1)

A 594 nm
B 640 nm
C 700 nm
D 494 nm

Answer:494 nm
18 Mg2+ is isoelectronic with
A Ca2+
B Na+
C Zn2+
D Cu2+

Answer: Na+
19 Which one of the following sets of ions represents a collection of isoelectronic species?
A K+, Cl–, Ca2+, Sc3+
B Ba2+, Sr2+, K+, S2–
C N3–, O2–, F–, S2–
D Li+, Na+, Mg2+, Ca2+

Answer:K+, Cl–, Ca2+, Sc3+
20 Consider the ground state of Cr atom (Z = 24). The numbers of electrons with the azimuthal quantum numbers, l = 1 and 2 are, respectively: [AIEEE 2004]
A 12 and 4
B 12 and 5
C 16 and 4
D 16 and 5

Answer:12 and 5

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