Atomic Structure · JEE Main previous year questions

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

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).

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.

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 : $\sqrt{3}=1.73$, $h=6.63\times 10^{-34}\text{ Js}$ ${\mathrm{m}}_{\mathrm{e}}=9.1\times 10^{-31}\text{ kg}$; $c=3.0\times 10^8{\text{ ms}}^{-1}$; $1\text{eV}=1.6\times 10^{-19}\text{ J}$ ]

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)

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

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

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

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) $[\text{Given : }\mathrm{h}=6.63\times 10^{-34}\mathrm{Js}]$

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

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 ${\Delta }_0<\mathrm{P}$

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, $2.303\frac{RT}{F}=0.06\mathrm{V}$; $E_{AgCl|Ag|C{\mathrm{l}}^{-}}^{\circ }=0.22\mathrm{V}$

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

The metal mainly used in devising photoelectric cells is :

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

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

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 ($h=6.63\times 10^{-34}\mathrm{J}\mathrm{s}$; $c=3\times 10^{8}m/s$) _______ $\times 10^{-21}\mathrm{J}$.

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.$4\pi a_0$

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.$[\mathrm{Xe}]4f^7\text{ and }[\mathrm{Xe}]4f^1$

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

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.$\frac{4a_0}{3}$

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

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

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

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.$\pi 2p_x$

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

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 $d_{xy}$

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.