CBSE Class 11 Chemistry Atomic Structure Worksheet

Question. When an electron in hydrogen atom is excited, from its 4^th to 5th stationary orbit, the change in angular momentum of electron is? (Planck’s constant: h = 6.6×10^–34 J–s)
a. 4.16×10^–34 J–s
b. 3.32×10^–34 J–s
c. 1.05×10^–34 J–s
d. 2.08×10^–34 J–s
Answer : C

Question. In hydrogen atom, if the difference in the energy of the electron in n = 2 and n = 3 orbits is E, the ionization energy of hydrogen atom is:
a. 13.2 E
b. 7.2 E
c. 5.6 E
d. 3.2 E
Answer : B

Question. Hydrogen atom in its ground state is excited by radiation of wavelength 975 Å. How many lines will be there in the emission spectrum?
a. 2
b. 4
c. 6
d. 8
Answer : C

Question. A photon of energy 12.4 eV is completely absorbed by a hydrogen atom initially in the ground state so that it is excited. The quantum number of the excited state is:
a. n =1
b. n= 3
c. n = 4
d. n = ∞
Answer : C

Question. The wave number of the energy emitted when electron comes from fourth orbit to second orbit in hydrogen is 20,397 cm^–1. The wave number of the energy for the same transition in He⁺ is:
a. 5,099 cm^–1
b. 20,497 cm^–1
c. 40,994 cm^–1
d. 81,998 cm^–1
Answer : D

Question. When radiation of wavelength λ is incident on a metallic surface the stopping potential is 4.8 volts. If the same surface is illuminated with radiation of double the wavelength, then the stopping potential becomes 1.6 volts. Then the threshold wavelength for the surface is?
a. 2λ
b. 4λ
c. 6λ
d. 8λ
Answer : B

Question. In Bohr model of hydrogen atom, the ratio of periods of revolution of an electron in n = 2 and n = 1 orbits is:
a. 2 : 1
b. 4 : 1
c. 8 : 1
d. 16 : 1
Answer : C

Question. Hydrogen atom emits blue light when it changes from n = 4 energy level to n = 2 level. Which colour of light would the atom emit when it changes from n = 5 level to n = 2 level?
a. Red
b. Yellow
c. Green
d. Violet
Answer : D

Question. A single electron orbits a stationary nucleus of charge +Ze, where Z is a constant. It requires 47.2 eV to excited electron from second Bohr orbit to third Bohr orbit. Find the value of Z:
a. 2
b. 5
c. 3
d. 4
Answer : B

Question. The first member of the Paschen series in hydrogen spectrum is of wavelength 18,800Å. The short wavelength limit of Paschen series is:
a. 1215 Å
b. 6560 Å
c. 8225 Å
d. 12850 Å
Answer : C

Question. The cut off wavelength of continuous X-ray from two coolidge tubes operating at 30 kV but using different target materials (molybdenum Z=42 and tungsten Z = 74) are:
a. 1Å, 3Å
b. 0.3 Å, 0.2 Å
c. 0.414 Å, 0.8 Å
d. 0.414 Å, 0.414 Å
Answer : D

Question. If the atom ₁₀₀Fm²⁵⁷ follows the Bohr model and the radius of ₁₀₀Fm²⁵⁷ is n times the Bohr radius, then find n:
a. 100
b. 200
c. 4
d. 1/4
Answer : D

Question. One would expect proton to have very large:
a. Ionization potential
b. Radius
c. Charge
d. Hydration energy
Answer : D

Question. The mass of 1 mole of electrons is:
a. 9.1x10−²⁸ g
b. 1.008mg
c. 0.55mg
d. 9.1x10⁻²⁷ g
Answer : C

Question. Energy of the electron in n^th orbit of hydrogen atom is given by E₂ = 13.6/n²,  eV. The amount of energy needed to transfer electron from first orbit to third orbit is:
a. 13.6 eV
b. 3.4 eV
c. 12.09 eV
d. 1.51 eV
Answer : C

Question. If the binding energy of the electron in a hydrogen atom is 13.6 eV, the energy required to remove the electron from the first excited state of Li⁺⁺ is:
a. 122.4 eV
b. 30.6 eV
c. 13.6 eV
d. 3.4 eV
Answer : B

Question. The ratio of the wavelengths for 2 → 1 transition in Li⁺⁺, He⁺ and H is:
a. 1 : 2 : 3
b. 1 : 4 : 9
c. 4 : 9 : 36
d. 3 : 2 : 1
Answer : C

Question. If scattering particles are 56 for 90º angle then this will be at 60º angle:
a. 224
b. 256
c. 98
d. 108
Answer : A

Question. What is the ratio of mass of an electron to the mass of a proton?
a. 1 : 2
b. 1 : 1
c. 1 : 1837
d. 1 : 3
Answer : C

Question. The nucleus of the element having atomic number 25 and atomic weight 55 will contain:
a. 25 protons and 30 neutrons
b. 25 neutrons and 30 protons
c. 55 protons
d. 55 neutrons
Answer : A

Question. In X-ray tube when the accelerating voltage V is halved, the difference between the wavelength of K_α line and minimum wavelength of continuous X-ray spectrum:
a. Remains constant
b. Becomes more than two times
c. Becomes half
d. Becomes less than two times
Answer : C

Question. A neutral atom (Atomic no. > 1) consists of:
a. Only protons
b. Neutrons + protons
c. Neutrons + electrons
d. Neutron + proton + electron
Answer : D

Question. The ratio of charge and mass would be greater for:
a. Proton
b. Electron
c. Neutron
d. Alpha
Answer : B

Question. Proton was discovered by?
a. Chadwick
b. Thomson
c. Goldstein
d. Bohr
Answer : C

Question. CO has same electrons as or the ion that is isoelectronic with CO is:
a. N₂⁺
b. CN⁻
c. O₂⁺
d. O₂⁻
Answer : B

Question. The most probable radius (in pm) for finding the electron in He⁺ is:
a. 0.0
b. 52.9
c. 26.5
d. 105.8
Answer : C

Question. The energy of second Bohr orbit of the hydrogen atom is –328 kJ mol^–1, hence the energy of fourth Bohr orbit would be:
a. – 41 kJ mol^–1
b. –1312 kJ mol^–1
c. –164 kJ mol^–1
d. – 82 kJ mol^–1
Answer : D

Question. The specific charge of proton is 9.6 x 10⁶ Ckg⁻¹ then for an α-particle it will be:
a. 38.4 x 10⁷ Ckg⁻¹
b. 19.2 x 10⁷ Ckg⁻¹
c. 2.4 x 10⁷ Ckg⁻¹
d. 4.8 x 10⁷ Ckg⁻¹
Answer : D

Question. If change in energy (ΔE) = 3 x 10^-8 J, h 6.64 10^-34 J-s and c = 3×10⁸ m/s, then wavelength of the light is:
a. 6.36 × 10³ Å
b. 6.36 × 10⁵ Å
c. 6.64 x 10^-8 Å 
d. 6.36 × 10¹⁸ Å
Answer : C

Question. The frequency corresponding to transition n = 2 to n = 1 in hydrogen atom is:
a. 15.66×10¹⁰ Hz
b. 24.66×10¹⁴ Hz
c. 30.57×10¹⁴ Hz
d. 40.57×10²⁴ Hz
Answer : B

Question. The frequency of radiation emitted when the electron falls from n = 4 to n = 1 in a hydrogen atom will be?
(Given ionization energy of H = 2.18 x 10^-18 J atom^-1 and h = 6.625 x 10-³⁴ Js)
a. 3.08 x 10¹⁵ s⁻¹
b. 2.00 x 10¹⁵ s⁻¹
c. 1.54 x 10¹⁵ s⁻¹
d. 1.03 x 10¹⁵ s⁻¹
Answer : A

Question. In the nucleus of ₂₀Ca⁴⁰ there are:
a. 40 protons and 20 electrons
b. 20 protons and 40 electrons
c. 20 protons and 20 neutrons
d. 20 protons and 40 neutrons
Answer : C

Question. Nitrogen atom has an atomic number of 7 and oxygen has an atomic number 8. The total number of electrons in a nitrate ion will be:
a. 8
b. 16
c. 32
d. 64
Answer : C

Question. Which among the following species have the same number of electrons in its outermost as well as penultimate shell?
a. Mg²⁺
b. 2O⁻
c. F⁻
d. Ca²⁺
Answer : D

Question. Number of neutrons in heavy hydrogen atom is:
a. 0
b. 1
c. 2
d. 3
Answer : B

Question. The spectrum of He is expected to be similar to:
a. H
b. Li⁺
c. Na
d. He⁺
Answer : B

Question. The uncertainty in the position of a moving bullet of mass 10 gm is 10^-5 m. Calculate the uncertainty in its velocity:
a. 5.2x10^-28 m/sec
b. 3.0x10^-28 m/sec
c. 5.2x10^-22 m/sec
d. 3x10^-22- m/sec
Answer : A

Question. Which quantum number is not related with Schrodinger equation?
a. Principal
b. Azimuthal
c. Magnetic
d. Spin
Answer : D

Question. According to Heisenberg’s uncertainty principle, the product of uncertainties in position and velocities for an electron of mass 9.1x10⁻³¹ kg is:
a. 3 2 1 2.8 10⁻³ m² s⁻¹
b. 5 2 1 3.8 10⁻⁵ m² s⁻¹
c. 5 2 1 5.8 10⁻⁵ m² s⁻¹
d. 6 2 1 6.8 10⁻⁶ m² s⁻¹
Answer : C

Question. Correct set of four quantum numbers for valence electron of rubidium (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 : A

Question. The maximum energy is present in any electron at:
a. Nucleus
b. Ground state
c. First excited state
d. Infinite distance from the nucleus
Answer : D

Question. The energy of electron in hydrogen atom in its grounds state is –13.6eV. The energy of the level corresponding to the quantum number equal to 5 is:
a. –0.54 eV
b. – 0.85 eV
c. – 0.64 eV
d. – 0.40 eV
Answer : A

Question. Which of the following transitions have minimum wavelength?
a. n₄ → n₁
b. n₂ → n₁
c. n₄ → n₂
d. n₃ → n₁
Answer : A

Question. An electron has kinetic energy 2.8 x 10^-23 J. de-Broglie wavelength will be nearly: (m_e = 9.1 x 10^-31 kg)
a. 9.28x10⁻⁴ m
b. 9.28x10⁻⁷ m
c. 9.28x10⁻⁸ m
d. 9.28x10⁻⁵ m
Answer : C

Question. Calculate de-Broglie wavelength of an electron travelling at 1% of the speed of light:
a. 2.73x10⁻²⁴
b. 2.42x10⁻¹⁰
c. 242.2x10⁻¹⁰
d. None of these
Answer : B

Question. The number of radial nodes of 3s and 2p orbitals are respectively:
a. 2, 0
b. 0, 2
c. 1, 2
d. 2, 1
Answer : A

Question. Which of the following ions is not having the configuration of neon?
a. F⁻
b. Mg⁺²
c. Na⁺
d. Cl⁻
Answer : D

Question. If the value of azimuthal quantum number is 3, the possible values of magnetic quantum number would be:
a. 0, 1, 2, 3
b. 0, – 1, – 2, – 3
c. 0, ± 1, ± 2, ± 3
d. ± 1, ± 2, ± 3
Answer : C

Question. The set of quantum numbers n = 3, l = 0,m = 0,s = −1/ 2 belongs to the element:
a. Mg
b. Na
c. Ne
d. F
Answer : A

Question. Which of the following are in the ascending order of wavelength?
a. H_α, H_β, H_γ… lines in Balmer series of hydrogen atom
b. Lyman limit, Balmer limit, Paschen limit in the hydrogen spectrum
c. Violet, blue, yellow, red colours in solar spectrum
d. None of these
Answer : B, C

Question. Continuous spectrum is produced by:
a. Incandescent electric bulb
b. sun
c. Hydrogen molecules
d. Na-vapour lamp
Answer : A, B

Question. A gas of monoatomic hydrogen is bombarded with a stream of electrons that have been accelerated from rest through a potential difference of 12.75 volt. In emission spectrum one can observe lines of:
a. Lyman series
b. Balmer series
c. Paschen series
d. Pfund series
Answer : A, B, C

Question. If the potential energy of the electron in the first allowed orbit in hydrogen atom is E, its:
a. Ionisation potential is –E/2
b. Kinetic energy is –E/2
c. Total energy is E/2
d. None of these true
Answer : A, B, C

Question. According to Bohr’s theory of the hydrogen atom, for the electron in the n^th allowed orbit, the:
a. Linear momentum is proportional to (1/n)
b. the radius is proportional to n
c. The kinetic energy is proportional to (1/n²)
d. The angular momentum is proportional to n
Answer : A, C, D

Question. Rutherford’s α– particle scattering experiment led to the following conclusion:
a. Atom has largely empty space
b. The centre of the atom has positively charged nucleus
c. The size of the nucleus is very small as compared to the size of the atom
d. The electrons revolve around the nucleus
Answer : A, B, C

Assertion and Reason

Note: Read the Assertion (A) and Reason (R) carefully to mark the correct option out of the options given below:
a. If both assertion and reason are true and the reason is the correct explanation of the assertion.
b. If both assertion and reason are true but reason is not the correct explanation of the assertion.
c. If assertion is true but reason is false.
d. If the assertion and reason both are false.
e. If assertion is false but reason is true.

Question. Assertion: Neutrons penetrate matter more readily as compared to protons.
Reason: Neutrons are slightly more massive than protons.
Answer : B

Question. Assertion: Bohr had to postulate that the electrons in stationary orbits around the nucleus do not radiate.
Reason: According to classical physics all moving electrons radiate.
Answer : B

Question. Assertion: The force of repulsion between atomic nucleus and α-particle varies with distance according to inverse square law.
Reason: Rutherford did α-particle scattering experiment.
Answer : B

Question. Assertion: The positively charged nucleus of an atom has a radius of almost 10^–15m.
Reason: In α-particle scattering experiment, the distance of closest approach for α-particles is ≃ 10^–15m.
Answer : A

Question. Assertion: According to classical theory, the proposed path of an electron in Rutherford atom model will be parabolic.
Reason: According to electromagnetic theory an accelerated particle continuously emits radiation.
Answer : E

Question. Assertion: Electrons in the atom are held due to coulomb forces.
Reason: The atom is stable only because the centripetal force due to Coulomb’s law is balanced by the centrifugal force.
Answer : C

Question. Assertion: The electron in the hydrogen atom passes from energy level n = 4 to the n = 1level. The maximum and minimum number of photon that can be emitted are six and one respectively.
Reason: The photons are emitted when electron make a transition from the higher energy state to the lower energy state.
Answer : B

Question. Assertion: 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.
Answer : B

Question. Assertion: It is essential that all the lines available in the emission spectrum will also be available in the absorption spectrum.
Reason: The spectrum of hydrogen atom is only absorption spectrum.
Answer : D

Question. Assertion: For the scattering of α-particles at a large angles, only the nucleus of the atom is responsible.
Reason: Nucleus is very heavy in comparison to electrons.
Answer : A

Comprehension Based

Paragraph -I

When a particle is restricted to move along x-axis between x = 0 and x = a, where a is of nanometer dimension, its energy can take only certain specific values. The allowed energies of the particle moving in such a restricted region, correspond to the formation of standing waves with nodes at its ends x = 0 and x
= a. The wavelength of this standing wave is related to the linear momentum p of the particle according to the de Broglie relation. The energy of the particle of mass m is related to its linear momentum as E = P2/2m Thus, the energy of the particle can be denoted by a quantum number n taking values 1, 2, 3, … (n = 1), called the ground state) corresponding to the number of loops in the standing wave. Use the model described above to answer the following three questions for a particle moving in the line x = 0 to x = a. [Take h = 6.6 × 10^–34 Js and e = 1.6 × 10^–19C]

Question. The allowed energy for the particle for a particular value of n is proportional to:
a. a^–2
b. a^–3/2
c. a^–1
d. a²
Answer : A

Question. If the mass of the particle is m = 1.0 × 10^–30kg and a = 6.6 nm, the energy of the particle in its ground state is closest to:
a. 0.8 meV
b. 8 meV
c. 80 meV
d. 800 meV
Answer : B

Question. The speed of the particle than can take distance values is proportional to:
a. n^–3/2
b. n^–1
c. n^1/2
d. n
Answer : D

Q1. What experiment led to the discovery of electrons? Draw a neat labeled diagram?

Q2. Write the difference b/w canal rays and cathode rays?

Q3. Explain with diagram Thomson’s Plum pudding model of an atom?

Q4. Explain Rutherford experiment with neat labeled diagram. Write its observations & conclusions.

Q5. Explain the draw backs of Rutherford’s Experiment.

Q6. Write the main postulates of Bohr’s model of an atom.

Q7. Explain the first model of an atom based on quantisation of energy.

Q8. Name two properties of light radiations which indicate its particles like nature.

Q9. Name two properties of electrons which indicate its wave nature.

Q10. Explain the following (i) Black – Body radiations (ii) Photo electric effect.

Q11. Why is photoelectric effect more common in alkali metals?

Q12. Draw graph between intensity & wavelength for black body radiation at 2 temperatures. T1 & T2 (T2 > T1). Interpret graph.

Q13. What do you mean by ‘Quantum’?

Q14. Define emission spectrum & Absorption spectrum?

Q15. What is the value of Rydberg’s constant in Joules.