Atomic Structure · JEE Main previous year questions

2023 20 questions

1. Q732023 · 13 Apr 2023 · Shift 1

   The energy of an electron in the first Bohr orbit of hydrogen atom is $-2.18\times 10^{-18}\text{ J}$. Its energy in the third Bohr orbit is ___________.

   1. A.One third of this value
   2. B.Three times of this value
   3. C.$\frac{1}{9}$ th of this value
   4. D.$\frac{1}{27}$ of this value
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   Answer: C

2. Q852023 · 13 Apr 2023 · Shift 2· Numerical answer

   The orbital angular momentum of an electron in $3s$ orbital is $\frac{xh}{2\pi }$. The value of $x$ is ___________ (nearest integer)

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   Answer: 0

3. Q662023 · 12 Apr 2023 · Shift 1

   Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: $5f$ electrons can participate in bonding to a far greater extent than $4f$ electrons Reason R: $5f$ orbitals are not as buried as $4f$ orbitals In the light of the above statements, choose the correct answer from the options given below

   1. A.Both A and R are true and R is the correct explanation of A
   2. B.Both A and R are true but R is NOT the correct explanation of A
   3. C.A is true but R is false
   4. D.A is false but R is true
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   Answer: A

4. Q832023 · 12 Apr 2023 · Shift 1· Numerical answer

   Values of work function (${\mathrm{W}}_0$) for a few metals are given below | Metal | Li | Na | K | Mg | Cu | Ag | | :--- | :--- | :--- | :--- | :--- | :--- | :--- | | ${\mathrm{W}}_0/\text{eV}$ | 2.42 | 2.3 | 2.25 | 3.7 | 4.8 | 4.3 | The number of metals which will show photoelectric effect when light of wavelength $400\text{ nm}$ falls on it is _________ Given: $h=6.6\times 10^{-34}\text{ J s}$ $c=3\times 10^8{\text{ ms}}^{-1}$ $e=1.6\times 10^{-19}\text{ C}$

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   Answer: 3

5. Q642023 · 11 Apr 2023 · Shift 1

   Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R : Assertion A : In the photoelectric effect, the electrons are ejected from the metal surface as soon as the beam of light of frequency greater than threshold frequency strikes the surface. Reason R : When the photon of any energy strikes an electron in the atom, transfer of energy from the photon to the electron takes place. In the light of the above statements, choose the most appropriate answer from the options given below :

   1. A.Both A and R are correct and R is the correct explanation of A
   2. B.A is not correct but R is correct
   3. C.A is correct but R is not correct
   4. D.Both A and R are correct but R is NOT the correct explanation of A
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   Answer: C

6. Q702023 · 11 Apr 2023 · Shift 2

   The magnetic moment is measured in Bohr Magneton (BM). Spin only magnetic moment of $\mathrm{Fe}$ in $[\mathrm{Fe}({\mathrm{H}}_2\mathrm{O}{)}_6{]}^{3+}$ and $[\mathrm{Fe}(\mathrm{CN}{)}_6{]}^{3-}$ complexes respectively is :

   1. A.$3.87\text{ B.M.}$ and $1.732\text{ B.M.}$
   2. B.$5.92\text{ B.M.}$ and $1.732\text{ B.M.}$
   3. C.$6.92\text{ B.M.}$ in both
   4. D.$4.89\text{ B.M.}$ and $6.92\text{ B.M.}$
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   Answer: B

7. Q852023 · 11 Apr 2023 · Shift 2· Numerical answer

   The number of correct statements from the following is _________. A. For $1s$ orbital, the probability density is maximum at the nucleus B. For $2s$ orbital, the probability density first increases to maximum and then decreases sharply to zero. C. Boundary surface diagrams of the orbitals encloses a region of $100\%$ probability of finding the electron. D. p and d-orbitals have 1 and 2 angular nodes respectively. E. probability density of p-orbital is zero at the nucleus

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   Answer: 3

8. Q812023 · 10 Apr 2023 · Shift 1· Numerical answer

   In potassium ferrocyanide, there are _________ pairs of electrons in the $t_{2g}$ set of orbitals.

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   Answer: 3

9. Q862023 · 8 Apr 2023 · Shift 2· Numerical answer

   The number of atomic orbitals from the following having 5 radial nodes is ____. 7s, 7p, 6s, 8p, 8d

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   Answer: 3

10. Q652023 · 6 Apr 2023 · Shift 2

    If the radius of the first orbit of hydrogen atom is ${\alpha }_0$, then de Broglie's wavelength of electron in $3^{\text{rd}}$ orbit is :

    1. A.$\frac{\pi {\alpha }_0}{6}$
    2. B.$3\pi {\alpha }_0$
    3. C.$6\pi {\alpha }_0$
    4. D.$\frac{\pi {\alpha }_0}{3}$
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    Answer: C

11. Q612023 · 1 Feb 2023 · Shift 1

    Which of the following complexes will show largest splitting of d-orbitals?

    1. A.$[\text{Fe}({\text{C}}_2{\text{O}}_4{)}_3{]}^{3-}$
    2. B.$[\text{Fe}(\text{CN}{)}_6{]}^{3-}$
    3. C.$[\text{Fe}({\text{NH}}_3{)}_6{]}^{3+}$
    4. D.$[{\text{FeF}}_6{]}^{3-}$
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    Answer: B

12. Q822023 · 1 Feb 2023 · Shift 1· Numerical answer

    Electrons in a cathode ray tube have been emitted with a velocity of $1000{\text{ m s}}^{-1}$. The number of following statements which is/are true about the emitted radiation is ________. Given : $\text{h}=6\times 10^{-34}\text{ J s},{\text{m}}_e=9\times 10^{-31}\text{ kg}$. (A) The de-Broglie wavelength of the electron emitted is $666.67\text{ nm}$. (B) The characteristic of electrons emitted depend upon the material of the electrodes of the cathode ray tube. (C) The cathode rays start from cathode and move towards anode. (D) The nature of the emitted electrons depends on the nature of the gas present in cathode ray tube.

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    Answer: 2

13. Q712023 · 31 Jan 2023 · Shift 1

    Which transition in the hydrogen spectrum would have the same wavelength as the Balmer type transition from $n=4$ to $n=2$ of ${\mathrm{He}}^{+}$ spectrum

    1. A.$n=3\text{ to }n=4$
    2. B.$n=2\text{ to }n=1$
    3. C.$n=1\text{ to }n=2$
    4. D.$n=1\text{ to }n=3$
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    Answer: B

14. Q652023 · 31 Jan 2023 · Shift 2

    Which of the following elements have half-filled f-orbitals in their ground state? $\left(\text{Given : atomic number }\mathrm{Sm}=62;\mathrm{Eu}=63;\mathrm{Tb}=65;\mathrm{Gd}=64,\mathrm{Pm}=61\right)$ A. $\mathrm{Sm}$ B. $\mathrm{Eu}$ C. $\mathrm{Tb}$ D. $\mathrm{Gd}$ E. $\mathrm{Pm}$ Choose the correct answer from the options given below :

    1. A.B and D only
    2. B.A and B only
    3. C.C and D only
    4. D.A and E only
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    Answer: A

15. Q672023 · 31 Jan 2023 · Shift 2

    Arrange the following orbitals in decreasing order of energy. A. $n=3,l=0,m=0$ B. $n=4,l=0,m=0$ C. $n=3,l=1,m=0$ D. $n=3,l=2,m=1$ The correct option for the order is :

    1. A.$\mathrm{B}>\mathrm{D}>\mathrm{C}>\mathrm{A}$
    2. B.$\mathrm{A}>\mathrm{C}>\mathrm{B}>\mathrm{D}$
    3. C.$\mathrm{D}>\mathrm{B}>\mathrm{A}>\mathrm{C}$
    4. D.$\mathrm{D}>\mathrm{B}>\mathrm{C}>\mathrm{A}$
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    Answer: D

16. Q692023 · 31 Jan 2023 · Shift 2

    Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R) Assertion (A): The first ionization enthalpy of 3 d series elements is more than that of group 2 metals Reason (R): In 3d series of elements successive filling of d-orbitals takes place. In the light of the above statements, choose the correct answer from the options given below :

    1. A.Both (A) and (R) are true and (R) is the correct explanation of (A)
    2. B.(A) is true but (R) is false
    3. C.Both (A) and (R) are true but (R) is not the correct explanation of (A)
    4. D.(A) is false but (R) is true
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    Answer: A

17. Q612023 · 29 Jan 2023 · Shift 2

    Given below are two statements : Statement I : The decrease in first ionization enthalpy from B to Al is much larger than that from Al to Ga. Statement II : The d orbitals in Ga are completely filled. In the light of the above statements, choose the most appropriate answer from the options given below

    1. A.Statement I is correct but statement II is incorrect
    2. B.Statement I is incorrect but statement II is correct
    3. C.Both the statements I and II are correct
    4. D.Both the statements I and II are incorrect
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    Answer: C

18. Q872023 · 29 Jan 2023 · Shift 2· Numerical answer

    Assume that the radius of the first Bohr orbit of hydrogen atom is $0.6\mathring{\mathrm{A}}$. The radius of the third Bohr orbit of $\mathrm{H}{\mathrm{e}}^{+}$ is ____ picometer. (Nearest Integer)

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    Answer: 270

19. Q852023 · 25 Jan 2023 · Shift 2· Numerical answer

    The number of given orbitals which have electron density along the axis is ____ ${\mathrm{p}}_{\mathrm{x}},{\mathrm{p}}_{\mathrm{y}},{\mathrm{p}}_{\mathrm{z}},{\mathrm{d}}_{\mathrm{xy}},{\mathrm{d}}_{\mathrm{yz}},{\mathrm{d}}_{\mathrm{xz}},{\mathrm{d}}_{{\mathrm{z}}^2},{\mathrm{d}}_{{\mathrm{x}}^2-{\mathrm{y}}^2}$

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    Answer: 5

20. Q632023 · 24 Jan 2023 · Shift 2

    What is the number of unpaired electron(s) in the highest occupied molecular orbital of the following species : ${\mathrm{N}}_2;{\mathrm{N}}_2^{+};{\mathrm{O}}_2;{\mathrm{O}}_2^{+}$ ?

    1. A.$0,1,0,1$
    2. B.$2,1,0,1$
    3. C.$0,1,2,1$
    4. D.$2,1,2,1$
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    Answer: C