Atomic Structure · JEE Main previous year questions

2020 11 questions

1. Q622020 · 6 Sept 2020 · Shift 2

   For a $d^4$ metal ion in an octahedral field, the correct electronic configuration is :

   1. A.$t_{2g}^4{e}_g^0$ when ${\Delta }_0<\mathrm{P}$
   2. B.$t_{2g}^3{e}_g^1$ when ${\Delta }_0>\mathrm{P}$
   3. C.$e_g^2{t}_{2g}^2$ when ${\Delta }_0<\mathrm{P}$
   4. D.$t_{2g}^3{e}_g^1$ when ${\Delta }_0<\mathrm{P}$
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   Answer: D

2. Q742020 · 3 Sept 2020 · Shift 1· Numerical answer

   The photoelectric current from Na (Work function, $w_0=2.3\mathrm{eV}$) is stopped by the output voltage of the cell $\mathrm{Pt}(\mathrm{s})\mid {\mathrm{H}}_2(\mathrm{g},1\mathrm{Bar})\mid \mathrm{HCl}(aq.,\mathrm{pH}=1)\mid \mathrm{AgCl}(\mathrm{s})\mid \mathrm{Ag}(\mathrm{s})$. The pH of aq. HCl required to stop the photoelectric current from $\mathrm{K}(w_0=2.25\mathrm{eV})$, all other conditions remaining the same, is _______ $\times 10^{-2}$ (to the nearest integer). Given, $2.303\frac{RT}{F}=0.06\mathrm{V}$; $E_{AgCl|Ag|C{\mathrm{l}}^{-}}^{\circ }=0.22\mathrm{V}$

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   Answer: 142

3. Q532020 · 3 Sept 2020 · Shift 2

   Consider the hypothetical situation where the azimuthal quantum number, $l$, takes values $0,1,2,\dots ,n+1$, where n is the principal quantum number. Then, the element with atomic number :

   1. A.13 has a half-filled valence subshell
   2. B.9 is the first alkali metal
   3. C.8 is the first noble gas
   4. D.6 has a 2p-valence subshell
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   Answer: A

4. Q702020 · 2 Sept 2020 · Shift 1

   The metal mainly used in devising photoelectric cells is :

   1. A.Na
   2. B.Rb
   3. C.Li
   4. D.Cs
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   Answer: D

5. Q552020 · 2 Sept 2020 · Shift 2

   The number of subshells associated with n = 4 and m = –2 quantum numbers is

   1. A.8
   2. B.2
   3. C.16
   4. D.4
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   Answer: B

6. Q722020 · 2 Sept 2020 · Shift 2· Numerical answer

   The work function of sodium metal is $4.41\times 10^{-19}\mathrm{J}$. If photons of wavelength 300 nm are incident on the metal, the kinetic energy of the ejected electrons will be ($h=6.63\times 10^{-34}\mathrm{J}\mathrm{s}$; $c=3\times 10^{8}m/s$) _______ $\times 10^{-21}\mathrm{J}$.

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   Answer: 222

7. Q662020 · 9 Jan 2020 · Shift 1

   The de Broglie wavelength of an electron in the 4th Bohr orbit is :

   1. A.$2\pi a_0$
   2. B.$6\pi a_0$
   3. C.$8\pi a_0$
   4. D.$4\pi a_0$
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   Answer: C

8. Q672020 · 9 Jan 2020 · Shift 1

   The electronic configurations of bivalent europium and trivalent cerium are (atomic number : Xe = 54, Ce = 58, Eu = 63)

   1. A.$[\mathrm{Xe}]4f^{7}6s^2\text{ and }[\mathrm{Xe}]4f^{2}6s^2$
   2. B.$[\mathrm{Xe}]4f^2\text{ and }[\mathrm{Xe}]4f^7$
   3. C.$[\mathrm{Xe}]4f^4\text{ and }[\mathrm{Xe}]4f^9$
   4. D.$[\mathrm{Xe}]4f^7\text{ and }[\mathrm{Xe}]4f^1$
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   Answer: D

9. Q642020 · 9 Jan 2020 · Shift 2

   The number of ${\mathrm{sp}}^2$ hybrid orbitals in a molecule of benzene is :

   1. A.24
   2. B.12
   3. C.6
   4. D.18
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   Answer: D

10. Q602020 · 8 Jan 2020 · Shift 2

    The radius of the second Bohr orbit, in terms of the Bohr radius, $a_0$, in ${\mathrm{Li}}^{2+}$ is :

    1. A.$\frac{2a_0}{9}$
    2. B.$\frac{2a_0}{3}$
    3. C.$\frac{4a_0}{9}$
    4. D.$\frac{4a_0}{3}$
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    Answer: D

11. Q682020 · 7 Jan 2020 · Shift 1

    The number of orbitals associated with quantum number $n=5$, $m_s=+\frac{1}{2}$ is :

    1. A.11
    2. B.25
    3. C.15
    4. D.50
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    Answer: B