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Class 11 chemistry MCQ Question of Structure of Atom with Answers?

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Class 11 Chemistry MCQ Questions of Structure of Atom with Answers also help for a quick revision to enhance subject knowledge in exam time. These MCQ Questions with Answers were prepared based on the most recent syllabus and exam pattern. Solving the MCQ Questions for Class 11 Chemistry with Answers can be help students will be aware of all the concepts.

Everything around us is formed of atoms. Atom is that the smallest unit of matter and has all the chemical properties of a matter. Atom includes a positively charged nucleus, which contains charged particles referred to as protons and neutral particles called neutrons.

By Solving MCQ Questions for class 11 chemistry on Structure of Atom students can check their level of preparation.

Practice MCQ Questions for class 11 Chemistry Chapter-Wise

1. The increasing order (lowest first) for the values of e/m (charge/mass) for

(a) e, p, n, α
(b) n, p, e, α
(c) n, p, α, e
(d) n, α, p, e

2. Which of the following statements in relation to the hydrogen atom is correct?

(a) 3s orbital is lower in energy than 3p orbital
(b) 3p orbital is lower in energy than 3d orbital
(c) 3s and 3p orbitals are of lower energy than 3d orbital
(d) 3s, 3p and 3d orbitals all have the same energy

3. The magnetic quantum number specifies

(a) Size of orbitals
(b) Shape of orbitals
(c) Orientation of orbitals
(d) Nuclear Stability

4. The electronic configuration of silver atom in ground state is

(a) [Kr]3d104s1
(b) [Xe]4f145d106s1
(c) [Kr]4d105s1
(d) [Kr]4d95s2

5. Which of the following element has least number of electrons in its M-shell?

(a) K
(b) Mn
(c) Ni
(d) Sc

6. In the ground state, an element has 13 electrons in its M-shell. The element is......

(a) Copper
(b) Chromium
(c) Nickel
(d) Iron

7. The electrons of the same orbitals can be distinguished by

(a) Principal quantum number
(b) Azimuthal quantum number
(c) Spin quantum number
(d) Magnetic quantum number

8. In Hydrogen atom, energy of first excited state is – 3.4 eV. Then find out KE of same orbit of Hydrogen atom

(a) 3.4 eV
(b) 6.8 eV
(c) -13.6 eV
(d) +13.6 eV

9. Which of the following statements does not form a part of Bohrs model of hydrogen atom?

(a) Energy of the electrons in the orbit is quantised
(b) The electron in the orbit nearest the nucleus has the lowest energy
(c) Electrons revolve in different orbits around the nucleus
(d) The position and velocity of the electrons in the orbit cannot be determined simultaneously

10. A sub-shell with n = 6 , l = 2 can accommodate a maximum of

(a) 12 electrons
(b) 36 electrons
(c) 10 electrons
(d) 72 electrons

11. Which of the following is never true for cathode rays?

(a) They are electromagnetic waves
(b) They produce heat.
(c) They produce mechanical pressure
(d) They possess kinetic energy

12. While performing cathode ray experiments, it was observed that there was no passage of electric current under normal conditions. Which of the following can account for this observation?

(a) Air is a poor conductor of electricity under normal conditions
(b) Carbon dioxide is present in air
(c) Dust particles are present in air
(d) None of the above

13. When beryllium is bombarded with alpha particles (Chadwick’s experiment) extremely penetrating radiations, which cannot be deflected by electrical or magnetic field are given out. These are

(a) A beam of neutrons
(b) Alpha rays
(c) A beam of neutrons and protons
(d) A beam of protons

14. Neutron is discovered by

(a) Chadwick
(b) Yukawa
(c) Rutherford
(d) Dalton

15. 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

16. Nucleons are

(a) neutrons + protons
(b) neutrons + protons + electrons
(c) neutrons + electrons
(d) only neutrons

17. How many unpaired electrons are present in Ni2+ cation (atomic number = 28)

(a) 0
(b) 2
(c) 4
(d) 6

18. Which type of radiation is not emitted by the electronic structure of atoms:

(a) Ultraviolet light
(b) X-rays
(c) Visible light
(d)  \(\gamma-\)rays

19. The maximum number of atomic orbitals associated with a principal quantum number 5 is

(a) 9
(b) 12
(c) 16
(d) 25

20. The total number of neutrons in dipositive zinc ions with mass number 70 is -

(a) 34
(b) 40
(c) 36
(d) 38

21. The wavelengths of two photons are 2000 Å and 4000 Å respectively. What is the ratio of their energies?

(a) 1/4
(b) 4
(c) 1/2
(d) 2

22. The number of electrons in one molecule of CO2 are - 

(a) 22
(b) 44
(c) 66
(d) 88

23. The ion that is isoelectronic with CO is-

(a) CN-
(b) O2+
(c) O2-
(d) N2+

24. The presence of one electron each in the three 2p sub-shell of nitrogen is explained by 

(a) Uncertainty principle
(b) Hund's rule
(c) Pauli's principle 
(d) Bohr's theory

25. Rutherford's scattering experiment is related to the size of the-

(a) Nucleus
(b) Atom
(c) Electron
(d) Neutron

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Answer :

1. Answer : (d) n, α, p, e

Explanation: Neutron has no charge, hence e/ m is zero for neutron. Next, a-particle (He2+ ) has very high mass compared to proton and electron, therefore very small e/m ratio. Proton and   electron have same charge (magnitude).

2. Answer : (d) 3s, 3p and 3d orbitals all have the same energy

Explanation: In a hydrogen atom, 3s,3p and 3d orbitals will have same energy as all orbitals belonging to the same shell have same energy in hydrogen atom.

3. Answer : (c) Orientation of orbitals

Explanation: Magnetic Quantum Number (ml) specifies the orientation in space of an orbital of a given energy (n) and shape (l). This number divides the subshell into individual orbitals which hold the electrons; there are 2l+1 orbitals in each subshell.

4. Answer : (c) [Kr]4d105s1

Explanation: The electronic configuration of Ag in ground state is [Kr]4d105s1

5. Answer : (a) K

Explanation: K = 19 = 1s22s22p63s23p64s1

3s23p6 = m-shell

= k has only 8 electrons in M shell

6. Answer : (b) Chromium

Explanation: Electrons in M shell (or 3rd shell) = 13

∴ Configuration of M shell : 3s23p63d5

Therefore, the element can be either Cr(Z = 24) or Mn (Z = 25). As Mn is not one of the options given, Cr is the correct answer.

7. Answer : (c) 

Explanation: Two electrons in same orbital have opposite spins as; +1/2 & -1/2. Therefore they can be distinguished from their spin quantum number.

8. Answer : (a) 3.4 eV

Explanation: The kinetic energy is equal to the negative of the total energy. The first excited state energy of orbital = -3.4 eV and The kinetic energy of same orbital = -(-3.4 eV) = 3.4 eV.

9. Answer : (d) 

Explanation: (i) The electrons in an atom revolve around the nucleus only in certain selected circular paths, called orbits. 

(ii) The energy is emitted or absorbed only when the electrons jump from one energy level to another. 

10. Answer : (c) 10 electrons

Explanation: n = 6, l = 2 means 6d → will have 5 orbitals. 

∴ max 10 electrons can be accommodate as each orbital can have maximum of 2 electrons. 

11. Answer : (a) They are electromagnetic waves

Explanation: Cathode rays are not electromagnetic wave because they do not have electric and magnetic components perpendicular to each other.

12. Answer : (a) Air is a poor conductor of electricity under normal conditions

Explanation: Air is a mixture of neutral or inert gases. Therefore it contains few or no charged particles or free ions for conduction of electricity. Hence, air is a poor conductor of electricity.

13. Answer : (a) A beam of neutrons

Explanation: As the neutron is a chargeless particle, hence, the beam of neutrons is not deflected by electrical or magnetic field.

14. Answer : (a) Chadwick

Explanation: In May 1932 James Chadwick announced that the core also contained a new uncharged particle, which he called the neutron.

15. Answer : (a) Overall neutrality of atom

Explanation: Only overall neutrality of an atom could be explained correctly by Thomson model of atom.

16. Answer : (a) neutrons + protons

Explanation: The nucleon number is equal to the total number of nucleons (protons and neutrons) in the nucleus of an atom.

17. Answer : (b) 2

Explanation: Nickel has two unpaired electrons in the 3d sublevel. When nickel ionizes to the +2 state it loses the two electrons in the 4s, so there are still two unpaired electrons in Ni2+

18. Answer : (d) \(\gamma-\)rays

Explanation: Gamma rays are not emitted by the electronic structure of atoms. They are photons, like light, thus they are neutral. Gamma rays are high energy (high frequency) electromagnetic radiation.

19. Answer : (d) 25

Explanation: Number of orbitals in a shell = n2 = (5)= 25

20. Answer : (b) 40

Explanation: Atomic weight =70

Atomic number =30

So the Number of neutrons 

= At. wt. − At. no. 

= 70− 30 

= 40

Hence, the total number of neutrons in dipositive zinc ions with the mass number 70 is 40.

21. Answer : (d) 2

Explanation: \(E_1=h.\frac{c}{\lambda_1}\)

\(E_2=h.\frac{c}{\lambda_2}\)

\(\frac{E_1}{E_2}=\frac{hc}{\lambda_1}\times\frac{\lambda_2}{\lambda_1}\)

= 4000/2000

= 2

22. Answer : (a) 22

Explanation: In a neutral atom, atomic number represents the number of protons inside the nucleus and equal number of electrons around it. Therefore, the number of total electrons in molecule of CO2

 = electrons present in one carbon atom + 2 x electrons present in one oxygen atom = 6 + 2 x 8 =  22.

23. Answer : (a) CN-

Explanation: Isoelectronic species are the having same number of electrons.

Number of electrons in CO = 6 + 8 = 14

O2- = 16 + 1 = 17

N2+ = 14 - 1 = 13

O2+ = 1 6 - 1 = 15

CN- = 6 + 7 + 1 = 14

Hence, CO isoelectronic with CN ion.

24. Answer : (b) Hund's rule

Explanation: The explanation for the presence of three unpaired electrons in the nitrogen atom can be given by Hund's rule. According to this rule, electron pairing in any orbital (s, p, d or f) cannot take place until each orbital of the same sublevel contains 1 electron. The electronic configuration of N is 1s22s22p3.2p orbital has 3 sub-levels each of which will contain one electron.

25. Answer : (a) Nucleus

Explanation: Rutherford`s scattering experiment is related to the size of the nucleus of an atom. The objective of experiment demonstrates the scattering of alpha particles by gold foil.

Click here to practice MCQ Questions for Structure of Atom class 11

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