Atomic Structure · JEE Main previous year questions

2021 21 questions

1. Q742021 · 1 Sept 2021 · Shift 2

   Identify the element for which electronic configuration in +3 oxidation state is $[\mathrm{Ar}]3{\mathrm{d}}^5$ :

   1. A.$\mathrm{Ru}$
   2. B.$\mathrm{Mn}$
   3. C.$\mathrm{Co}$
   4. D.$\mathrm{Fe}$
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   Answer: D

2. Q862021 · 1 Sept 2021 · Shift 2· Numerical answer

   A $50\mathrm{watt}$ bulb emits monochromatic red light of wavelength of $795\mathrm{nm}$. The number of photons emitted per second by the bulb is $x\times 10^{20}$. The value of x is ____. [Given : $h=6.63\times 10^{-34}\mathrm{Js}$ and $c=3.0\times 10^8\mathrm{m}{\mathrm{s}}^{-1}$]

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   Answer: 2

3. Q842021 · 26 Aug 2021 · Shift 2· Numerical answer

   A metal surface is exposed to 500 nm radiation. The threshold frequency of the metal for photoelectric current is $4.3\times 10^{14}\text{ Hz}$. The velocity of ejected electron is ___________ $\times 10^5{\text{ ms}}^{-1}$ (Nearest integer) [$\text{Use : }h=6.63\times 10^{-34}\text{ Js}$, $m_e=9.0\times 10^{-31}\text{ kg}$]

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   Answer: 5

4. Q632021 · 27 Jul 2021 · Shift 2

   Given below are two statements : Statement I : Hyperconjugation is a permanent effect. Statement II : Hyperconjugation in ethyl cation $\left(C{H}_3-\stackrel{+}{C}{H}_2\right)$ involves the overlapping of $C_{s{p}^2}-H_{1s}$ bond with empty 2p orbital of other carbon. Choose the correct option :

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

5. Q742021 · 27 Jul 2021 · Shift 2

   Match List - I with List - II : | | List - I | | List - II | |---|---|---|---| | (a) | Li | (i) | photoelectric cell | | (b) | Na | (ii) | absorbent of $C{O}_2$ | | (c) | K | (iii) | coolant in fast breeder nuclear reactor | | (d) | Cs | (iv) | treatment of cancer | | | | (v) | bearings for motor engines | Choose the correct answer from the options given below :

   1. A.(a) - (v), (b) - (i), (c) - (ii), (d) - (iv)
   2. B.(a) - (v), (b) - (ii), (c) - (iv), (d) - (i)
   3. C.(a) - (iv), (b) - (iii), (c) - (i), (d) - (ii)
   4. D.(a) - (v), (b) - (iii), (c) - (ii), (d) - (i)
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   Answer: D

6. Q852021 · 27 Jul 2021 · Shift 2· Numerical answer

   The total number of electrons in all bonding molecular orbitals of $O_2^{2-}$ is __________. (Round off to the nearest integer)

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   Answer: 10

7. Q822021 · 25 Jul 2021 · Shift 2· Numerical answer

   An accelerated electron has a speed of $5\times 10^6\mathrm{m}{\mathrm{s}}^{-1}$ with an uncertainty of 0.02%. The uncertainty in finding its location while in motion is $x\times 10^{-9}$ m. The value of x is ____. (Nearest integer) [Use mass of electron = $9.1\times 10^{-31}$ kg, h = $6.63\times 10^{-34}$ Js, $\pi$ = 3.14]

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   Answer: 58

8. Q832021 · 25 Jul 2021 · Shift 2· Numerical answer

   Number of electrons present in 4f orbital of $\mathrm{H}{\mathrm{o}}^{3+}$ ion is ____. (Given Atomic No. of Ho = 67)

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   Answer: 10

9. Q662021 · 22 Jul 2021 · Shift 2

   Match List-I with List-II : $$\begin{array}{llll}& \text{List-I}& & \text{List-II}\\ & \text{(Species)}& & \text{(Hybrid Orbitals)}\\ \text{(a)}& \mathrm{S}{\mathrm{F}}_4& \text{(i)}& \mathrm{s}{\mathrm{p}}^3{\mathrm{d}}^2\\ \text{(b)}& \mathrm{I}{\mathrm{F}}_5& \text{(ii)}& {\mathrm{d}}^2\mathrm{s}{\mathrm{p}}^3\\ \text{(c)}& \mathrm{N}{\mathrm{O}}_2^{+}& \text{(iii)}& \mathrm{s}{\mathrm{p}}^3\mathrm{d}\\ \text{(d)}& \mathrm{N}{\mathrm{H}}_4^{+}& \text{(iv)}& \mathrm{s}{\mathrm{p}}^3\\ & & \text{(v)}& \mathrm{sp}\end{array}$$ Choose the correct answer from the options given below :

   1. A.(a)-(i), (b)-(ii), (c)-(v) and (d)-(iii)
   2. B.(a)-(ii), (b)-(i), (c)-(iv) and (d)-(v)
   3. C.(a)-(iii), (b)-(i), (c)-(v) and (d)-(iv)
   4. D.(a)-(iv), (b)-(iii), (c)-(ii) and (d)-(v)
   Show answer

   Answer: C

10. Q752021 · 22 Jul 2021 · Shift 2

    Match List-I with List-II $$\begin{array}{llll}& \text{List-I (Elements)}& & \text{List-II (Properties)}\\ \text{(a)}& \text{Ba}& \text{(i)}& \text{Organic solvent soluble compounds}\\ \text{(b)}& \text{Ca}& \text{(ii)}& \text{Outer electronic configuration }6s^2\\ \text{(c)}& \text{Li}& \text{(iii)}& \text{Oxalate insoluble in water}\\ \text{(d)}& \text{Na}& \text{(iv)}& \text{Formation of very strong monoacidic base}\end{array}$$ Choose the correct answer from the options given below :

    1. A.(a)-(ii), (b)-(iii), (c)-(i) and (d)-(iv)
    2. B.(a)-(iv), (b)-(i), (c)-(ii) and (d)-(iii)
    3. C.(a)-(iii), (b)-(ii), (c)-(iv) and (d)-(i)
    4. D.(a)-(i), (b)-(iv), (c)-(ii) and (d)-(iii)
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    Answer: A

11. Q872021 · 22 Jul 2021 · Shift 2· Numerical answer

    Number of electrons that Vanadium (Z = 23) has in p-orbitals is equal to _____________

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    Answer: 12

12. Q832021 · 20 Jul 2021 · Shift 1· Numerical answer

    The Azimuthal quantum number for the valence electrons of ${\text{Ga}}^{+}$ ion is ________. (Atomic number of $\text{Ga}=31$)

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    Answer: 0

13. Q712021 · 18 Mar 2021 · Shift 1

    A certain orbital has no angular nodes and two radial nodes. The orbital is :

    1. A.2s
    2. B.3s
    3. C.3p
    4. D.2p
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    Answer: B

14. Q812021 · 18 Mar 2021 · Shift 1· Numerical answer

    AX is a covalent diatomic molecule where A and X are second row elements of periodic table. Based on Molecular orbital theory, the bond order of AX is 2.5. The total number of electrons in AX is __________. (Round off to the Nearest Integer).

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    Answer: 15

15. Q692021 · 18 Mar 2021 · Shift 2

    Given below are two statements : Statement I : Bohr's theory accounts for the stability and line spectrum of $\mathrm{L}{\mathrm{i}}^{+}$ ion. Statement II : Bohr's theory was unable to explain the splitting of spectral lines in the presence of a magnetic field. In the light of the above statements, choose the most appropriate answer from the options given below :

    1. A.Statement I is false but statement II is true.
    2. B.Both statement I and statement II are true.
    3. C.Statement I is true but statement II is false.
    4. D.Both statement I and statement II are false.
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    Answer: A

16. Q882021 · 16 Mar 2021 · Shift 1· Numerical answer

    When light of wavelength 248 nm falls on a metal of threshold energy 3.0 eV, the de-Broglie wavelength of emitted electrons is _______ $\text{A˚}$. (Round off to the Nearest Integer). [ Use : $\sqrt{3}=1.73$, $h=6.63\times 10^{-34}\text{ Js}$ ${\mathrm{m}}_{\mathrm{e}}=9.1\times 10^{-31}\text{ kg}$; $c=3.0\times 10^8{\text{ ms}}^{-1}$; $1\text{eV}=1.6\times 10^{-19}\text{ J}$ ]

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    Answer: 9

17. Q642021 · 26 Feb 2021 · Shift 1

    Match List - I with List - II. | List I (Electronic configuration) | List II (${\Delta }_{i}H\text{ in }\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$) | | :--- | :--- | | (a) $1s^{2}2s^2$ | (i) 801 | | (b) $1s^{2}2s^{2}2p^4$ | (ii) 899 | | (c) $1s^{2}2s^{2}2p^3$ | (iii) 1314 | | (d) $1s^{2}2s^{2}2p^1$ | (iv) 1402 | Choose the most appropriate answer from the options given below :

    1. A.(a) $\to$ (i), (b) $\to$ (iii), (c) $\to$ (iv), (d) $\to$ (ii)
    2. B.(a) $\to$ (iv), (b) $\to$ (i), (c) $\to$ (ii), (d) $\to$ (iii)
    3. C.(a) $\to$ (ii), (b) $\to$ (iii), (c) $\to$ (iv), (d) $\to$ (i)
    4. D.(a) $\to$ (i), (b) $\to$ (iv), (c) $\to$ (iii), (d) $\to$ (ii)
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    Answer: C

18. Q752021 · 26 Feb 2021 · Shift 1

    The orbital having two radial as well as two angular nodes is :

    1. A.3p
    2. B.5d
    3. C.4d
    4. D.4f
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    Answer: B

19. Q652021 · 26 Feb 2021 · Shift 2

    Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : In $\mathrm{Tl}{\mathrm{I}}_3$, isomorphous to $\mathrm{Cs}{\mathrm{I}}_3$, the metal is present in +1 oxidation state. Reason R : Tl metal has fourteen f electrons in its electronic configuration. In the light of the above statements, choose the most appropriate answer from the options given below :

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

20. Q882021 · 26 Feb 2021 · Shift 2· Numerical answer

    A ball weighing 10 g is moving with a velocity of $90\mathrm{m}{\mathrm{s}}^{-1}$. If the uncertainty in its velocity is 5%, then the uncertainty in its position is _________ $\times 10^{-33}\mathrm{m}$. (Rounded off to the nearest integer) $[\text{Given : }\mathrm{h}=6.63\times 10^{-34}\mathrm{Js}]$

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    Answer: 1

21. Q892021 · 25 Feb 2021 · Shift 2· Numerical answer

    Among the following, number of metal/s which can be used as electrodes in the photoelectric cell is _________. (Integer answer) (A) Li (B) Na (C) Rb (D) Cs

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    Answer: 1