Atomic Structure · JEE Main previous year questions

Correct statements for an element with atomic number 9 are: A. There can be 5 electrons for which $m_s=+\frac{1}{2}$ and 4 electrons for which $m_s=-\frac{1}{2}$. B. There is only one electron in $p_z$ orbital. C. The last electron goes to orbital with $n=2$ and $l=1$. D. The sum of angular nodes of all the atomic orbitals is 1. Choose the correct answer from the options given below:

1. A.A and B Only
2. B.A, C and D Only
3. C.A and C Only
4. D.C and D Only

The energy of an electron in the first Bohr orbit of the H-atom is -13.6 eV. The magnitude of energy value of an electron in the first excited state of $\mathrm{B}{\mathrm{e}}^{3+}$ is ____ eV (nearest integer value).

Which one of the following about an electron occupying the 1 s orbital in a hydrogen atom is incorrect? (Bohr's radius is represented by $a_0$)

1. A.The probability density of finding the electron is maximum at the nucleus
2. B.The total energy of the electron is maximum when it is at a distance $a_0$ from the nucleus
3. C.The electron can be found at a distance $2a_0$ from the nucleus
4. D.The 1 s orbital is spherically symmetrical

Given below are two statements: Statement I: Nitrogen forms oxides with +1 to +5 oxidation states due to the formation of $\mathrm{p}\pi -\mathrm{p}\pi$ bond with oxygen. Statement II: Nitrogen does not form halides with +5 oxidation state due to the absence of d-orbital in it. In the light of given statements, choose the correct answer from the options given below.

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

1. A.Both Statement I and Statement II are correct
2. B.Both Statement I and Statement II are incorrect
3. C.Statement I is correct but Statement II is incorrect
4. D.Statement I is incorrect but Statement II is correct

Consider the ground state of chromium atom ($Z=24$). How many electrons are with Azimuthal quantum number $l=1$ and $l=2$ respectively ?

1. A.16 and 5
2. B.12 and 5
3. C.12 and 4
4. D.16 and 4

Which of the following postulate of Bohr's model of hydrogen atom is not in agreement with quantum mechanical model of an atom?

1. A.The electron in a H atom's stationary state moves in a circle around the nucleus.
2. B.An atom can take only certain distinct energies $E_1,E_2,E_3$, etc. These allowed states of constant energy are called the stationary states of atom.
3. C.An atom in a stationary state does not emit electromagnetic radiation as long as it stays in the same state.
4. D.When an electron makes a transition from a higher energy stationary state to a lower energy stationary state, then it emits a photon of light.

For electrons in ' 2 s ' and ' 2 p ' orbitals, the orbital angular momentum values, respectively are:

1. A.$0$ and $\sqrt{6}\frac{h}{2\pi }$
2. B.$0$ and $\sqrt{2}\frac{h}{2\pi }$
3. C.$\sqrt{2}\frac{h}{2\pi }$ and $0$
4. D.$\frac{h}{2\pi }$ and $\sqrt{2}\frac{h}{2\pi }$

According to Bohr's model of hydrogen atom, which of the following statement is incorrect?

1. A.Radius of $4^{\mathrm{th}}$ orbit is four times larger than that of $2^{\mathrm{nd}}$ orbit
2. B.Radius of $8^{\mathrm{th}}$ orbit is four times larger than that of $4^{\mathrm{th}}$ orbit
3. C.Radius of $6^{\mathrm{th}}$ orbit is three times larger than that of $4^{\mathrm{th}}$ orbit
4. D.Radius of $3^{\mathrm{rd}}$ orbit is nine times larger than that of $1^{\mathrm{st}}$ orbit

A transition metal (M) among $\mathrm{Mn},\mathrm{Cr},\mathrm{Co}$ and $\mathrm{Fe}$ has the highest standard electrode potential $({\mathrm{M}}^{3+}/{\mathrm{M}}^{2+})$. It forms a metal complex of the type $[\mathrm{M}(\mathrm{CN}{)}_6{]}^{4-}$. The number of electrons present in the ${\mathrm{e}}_{\mathrm{g}}$ orbital of the complex is _________ .

Electronic configuration of four elements A, B, C and D are given below : (A) $1s^{2}2s^{2}2p^3$ (B) $1s^{2}2s^{2}2p^4$ (C) $1s^{2}2s^{2}2p^5$ (D) $1s^{2}2s^{2}2p^2$ Which of the following is the correct order of increasing electronegativity (Pauling's scale)?

1. A.$\mathrm{D}<\mathrm{A}<\mathrm{B}<\mathrm{C}$
2. B.$\mathrm{A}<\mathrm{B}<\mathrm{C}<\mathrm{D}$
3. C.$\mathrm{A}<\mathrm{C}<\mathrm{B}<\mathrm{D}$
4. D.$\mathrm{A}<\mathrm{D}<\mathrm{B}<\mathrm{C}$

1. A.(A) and (B) only
2. B.(B) and (D) only
3. C.(C) and (D) only
4. D.(A), (B) and (C) only

The d-orbital electronic configuration of the complex among $[\mathrm{Co}(\mathrm{en}{)}_3{]}^{3+}$, $[\mathrm{Co}{\mathrm{F}}_6{]}^{3-}$, $[\mathrm{Mn}({\mathrm{H}}_2\mathrm{O}{)}_6{]}^{2+}$ and $[\mathrm{Zn}({\mathrm{H}}_2\mathrm{O}{)}_6{]}^{2+}$ that has the highest CFSE is :

1. A.$t_{2g}^6{e}_g^0$
2. B.$t_{2g}^3{e}_g^2$
3. C.$t_{2g}^4{e}_g^2$
4. D.$t_{2g}^6{e}_g^4$

1. A.
2. B.
3. C.
4. D.

Given below are two statements : Statement (I) : It is impossible to specify simultaneously with arbitrary precision, both the linear momentum and the position of a particle. Statement (II) : If the uncertainty in the measurement of position and uncertainty in measurement of momentum are equal for an electron, then the uncertainty in the measurement of velocity is $⩾\sqrt{\frac{h}{\pi }}\times \frac{1}{2m}$. In the light of the above statements, choose the correct 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.Both Statement I and Statement II are false
4. D.Statement I is true but Statement II is false

In a multielectron atom, which of the following orbitals described by three quantum numbers will have same energy in absence of electric and magnetic fields? A. $n=1,l=0,m_l=0$ B. $n=2,l=0,m_l=0$ C. $n=2,l=1,m_l=1$ D. $n=3,l=2,m_l=1$ E. $n=3,l=2,m_l=0$ Choose the correct answer from the options given below:

1. A.B and C Only
2. B.C and D Only
3. C.A and B Only
4. D.D and E Only

Which of the following linear combination of atomic orbitals will lead to formation of molecular orbitals in homonuclear diatomic molecules [internuclear axis in $z$-direction] ? A. $2p_z$ and $2p_x$ B. $2\mathrm{s}$ and $2p_x$ C. $3d_{xy}$ and $3d_{x^2-y^2}$ D. $2\mathrm{s}$ and $2p_z$ E. $2p_z$ and $3d_{x^2-y^2}$ Choose the correct answer from the options given below:

1. A.D Only
2. B.E Only
3. C.C and D Only
4. D.A and B Only

Which of the following statements are NOT true about the periodic table? A. The properties of elements are function of atomic weights. B. The properties of elements are function of atomic numbers. C. Elements having similar outer electronic configurations are arranged in same period. D. An element's location reflects the quantum numbers of the last filled orbital. E. The number of elements in a period is same as the number of atomic orbitals available in energy level that is being filled. Choose the correct answer from the options given below:

1. A.A, C and E Only
2. B.A and E Only
3. C.B, C and E Only
4. D.D and E Only

For hydrogen atom, the orbital/s with lowest energy is/are : (A) $4s$ (B) $3p_x$ (C) $3{\mathrm{d}}_{x^2-y^2}$ (D) $3{\mathrm{d}}_{z^2}$ (E) $4p_z$ Choose the correct answer from the options given below :

1. A.(A) only
2. B.(B) only
3. C.(B), (C) and (D) only
4. D.(A) and (E) only

Given below are two statements : Statement (I) : For a given shell, the total number of allowed orbitals is given by $n^2$. Statement (II) : For any subshell, the spatial orientation of the orbitals is given by $-l$ to $+l$ values including zero. In the light of the above statements, choose the correct answer from the options given below :

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

The electronic configuration of $\mathrm{Cu}(\mathrm{II})$ is $3{\text{ d}}^9$ whereas that of $\mathrm{Cu}(\mathrm{I})$ is $3{\text{ d}}^{10}$. Which of the following is correct?

1. A.$\mathrm{Cu}(\mathrm{II})$ is more stable
2. B.$\mathrm{Cu}(\mathrm{II})$ is less stable
3. C.$\mathrm{Cu}(\mathrm{I})$ and $\mathrm{Cu}(\mathrm{II})$ are equally stable
4. D.Stability of $\mathrm{Cu}(\mathrm{I})$ and $\mathrm{Cu}(\mathrm{II})$ depends on nature of copper salts

Compare the energies of following sets of quantum numbers for multielectron system. (A) $n=4,l=1$ (B) $n=4,l=2$ (C) $n=3,l=1$ (D) $n=3,l=2$ (E) $n=4,l=0$ Choose the correct answer from the options given below :

1. A.(E) > (C) > (A) > (D) > (B)
2. B.(B) > (A) > (C) > (E) > (D)
3. C.(C) < (E) < (D) < (A) < (B)
4. D.(E) < (C) < (D) < (A) < (B)

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : ${\mathrm{S}}_{\mathrm{N}}2$ reaction of ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{C}{\mathrm{H}}_2\mathrm{Br}$ occurs more readily than the ${\mathrm{S}}_{\mathrm{N}}2$ reaction of $\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{Br}$. Reason (R) : The partially bonded unhybridized p-orbital that develops in the trigonal bipyramidal transition state is stabilized by conjugation with the phenyl ring. 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 but (R) is not the correct explanation of (A)
2. B.Both (A) and (R) are correct and (R) is the correct explanation of (A)
3. C.(A) is not correct but (R) is correct
4. D.(A) is correct but (R) is not correct

Match List I with List II $$\begin{array}{llll}& \text{LIST I (Element)}& & \text{LIST II (Electronic Configuration)}\\ \text{A.}& \mathrm{N}& \text{I.}& [\mathrm{Ar}]3{\mathrm{d}}^{10}4{\mathrm{s}}^{2}4{\mathrm{p}}^5\\ \text{B.}& \mathrm{S}& \text{II.}& [\mathrm{Ne}]3{\mathrm{s}}^{2}3{\mathrm{p}}^4\\ \text{C.}& \mathrm{Br}& \text{III.}& [\mathrm{He}]2{\mathrm{s}}^{2}2{\mathrm{p}}^3\\ \text{D.}& \mathrm{Kr}& \text{IV.}& [\mathrm{Ar}]3{\mathrm{d}}^{10}4{\mathrm{s}}^{2}4{\mathrm{p}}^6\end{array}$$ Choose the correct answer from the options given below:

1. A.A-IV, B-III, C-II, D-I
2. B.A-I, B-IV, C-III, D-II
3. C.A-III, B-II, C-I, D-IV
4. D.A-II, B-I, C-IV, D-III

The electronic configuration of Einsteinium is : (Given atomic number of Einsteinium $=99$)

1. A.$[\mathrm{Rn}]5{\mathrm{f}}^{13}6{\mathrm{d}}^{0}7{\mathrm{s}}^2$
2. B.$[\mathrm{Rn}]5{\mathrm{f}}^{12}6{\mathrm{d}}^{0}7{\mathrm{s}}^2$
3. C.$[\mathrm{Rn}]5{\mathrm{f}}^{11}6{\mathrm{d}}^{0}7{\mathrm{s}}^2$
4. D.$[\mathrm{Rn}]5{\mathrm{f}}^{10}6{\mathrm{d}}^{0}7{\mathrm{s}}^2$