Atomic Structure · JEE Main previous year questions

2019 10 questions

1. Q642019 · 12 Apr 2019 · Shift 2

   Among the following, the energy of 2s orbital is lowest in :

   1. A.Li
   2. B.H
   3. C.Na
   4. D.K
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   Answer: D

2. Q792019 · 10 Apr 2019 · Shift 1

   During the change of ${\mathrm{O}}_2$ to ${\mathrm{O}}_2^{-}$ , the incoming electron goes to the orbital :

   1. A.$\pi 2p_y$
   2. B.${\sigma }^{\ast }2p_z$
   3. C.${\pi }^{\ast }2p_x$
   4. D.$\pi 2p_x$
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   Answer: C

3. Q712019 · 10 Apr 2019 · Shift 2

   The ratio of the shortest wavelength of two spectral series of hydrogen spectrum is found to be about 9. The spectral series are :

   1. A.Paschen and Pfund
   2. B.Balmer and Brackett
   3. C.Lyman and Paschen
   4. D.Brackett and Pfund
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   Answer: C

4. Q622019 · 9 Apr 2019 · Shift 1

   The degenerate orbitals of $[\mathrm{Cr}({\mathrm{H}}_2\mathrm{O}{)}_6{]}^{3+}$ are :

   1. A.$d_{z^2}$ and $d_{xz}$
   2. B.$d_{xz}$ and $d_{yz}$
   3. C.$d_{yz}$ and $d_{z^2}$
   4. D.$d_{x^2-y^2}$ and $d_{xy}$
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   Answer: B

5. Q642019 · 9 Apr 2019 · Shift 2

   Which one of the following about an electron occupying the 1s orbital in a hydrogen atom is incorrect ? (The Bohr radius is represented by ${\mathrm{a}}_0$)

   1. A.The probability density of finding the electron is maximum at the nucleus.
   2. B.The electron can be found at a distance $2{\mathrm{a}}_0$ from the nucleus
   3. C.The total energy of the electron is maximum when it is at a distance ${\mathrm{a}}_0$ from the nucleus.
   4. D.The magnitude of potential energy is double that of its kinetic energy on an average.
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   Answer: C

6. Q692019 · 12 Jan 2019 · Shift 2

   If the de Broglie wavelength of the electron in $n^{th}$ Bohr orbit in a hydrogenic atom is equal to $1.5\pi a_0$ ($a_0$ is Bohr radius), then the value of n/z is -

   1. A.0.75
   2. B.0.40
   3. C.1.50
   4. D.1.0
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   Answer: A

7. Q612019 · 11 Jan 2019 · Shift 2

   The correct option with respect to the Pauling electronegativity values of the element is :

   1. A.Ga < Ge
   2. B.Si < Al
   3. C.Te > Se
   4. D.P > S
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   Answer: A

8. Q662019 · 11 Jan 2019 · Shift 2

   The de Broglie wavelength $(\lambda )$ associated with a photoelectron varies with the frequency $(\nu )$ of the incident radiation as, [${\nu }_0$ is threshold frequency] :

   1. A.$\lambda \propto \frac{1}{(\nu -{\nu }_0{)}^{\frac{3}{2}}}$
   2. B.$\lambda \propto \frac{1}{(\nu -{\nu }_0{)}^{\frac{1}{4}}}$
   3. C.$\lambda \propto \frac{1}{(\nu -{\nu }_0)}$
   4. D.$\lambda \propto \frac{1}{(\nu -{\nu }_0{)}^{\frac{1}{2}}}$
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   Answer: D

9. Q732019 · 9 Jan 2019 · Shift 1

   According to molecular orbital theory, which of the following is true with respect to $\mathrm{L}{\mathrm{i}}_2^{+}$ and $\mathrm{L}{\mathrm{i}}_2^{-}$ ?

   1. A.$\mathrm{L}{\mathrm{i}}_2^{+}$ is unstable and $\mathrm{L}{\mathrm{i}}_2^{-}$ is stable
   2. B.$\mathrm{L}{\mathrm{i}}_2^{+}$ is stable and $\mathrm{L}{\mathrm{i}}_2^{-}$ unstable
   3. C.Both are stable
   4. D.Both are unstable
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   Answer: C

10. Q752019 · 9 Jan 2019 · Shift 1

    For emission line of atomic hydrogen from $n_i=8$ to $n_f=n$, the plot of wave number $(\bar{\nu })$ against $\left(\frac{1}{n^2}\right)$ will be (The Rydberg constant, ${\mathrm{R}}_{\mathrm{H}}$ is in wave number unit)

    1. A.Linear with intercept $-{\mathrm{R}}_{\mathrm{H}}$
    2. B.Non linear
    3. C.Linear with slope ${\mathrm{R}}_{\mathrm{H}}$
    4. D.Linear with slope $-{\mathrm{R}}_{\mathrm{H}}$
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    Answer: C