1
JEE Main 2023 (Online) 31st January Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
Which of the following elements have half-filled f-orbitals in their ground state?

(Given : atomic number $\mathrm{Sm}=62 ; \mathrm{Eu}=63 ; \mathrm{Tb}=65 ; \mathrm{Gd}=64, \mathrm{Pm}=61$ )

A. $\mathrm{Sm}$

B. Eu

C. $\mathrm{Tb}$

D. Gd

E. $\mathrm{Pm}$

Choose the correct answer from the options given below :
A
B and D only
B
A and $B$ only
C
$C$ and $\mathrm{D}$ only
D
A and E only
2
JEE Main 2023 (Online) 31st January Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R)

Assertion (A): The first ionization enthalpy of $3 \mathrm{~d}$ series elements is more than that of group 2 metals

Reason (R): In 3d series of elements successive filling of d-orbitals takes place.

In the light of the above statements, choose the correct answer from the options given below :
A
Both (A) and (R) are true and (R) is the correct explanation of (A)
B
(A) is true but (R) is false
C
Both (A) and (R) are true but $(\mathbf{R})$ is not the correct explanation of (A)
D
(A) is false but (R) is true
3
JEE Main 2023 (Online) 31st January Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

The correct increasing order of the ionic radii is

A
$$\mathrm{Cl^- < Ca^{2+} < K^+ < S^{2-}}$$
B
$$\mathrm{K^+ < S^{2-} < Ca^{2+} < Cl^-}$$
C
$$\mathrm{Ca^{2+} < K^+ < Cl^- < S^{2-}}$$
D
$$\mathrm{S^{2-} < Cl^- < Ca^{2+} < K^+}$$
4
JEE Main 2023 (Online) 30th January Evening Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
Bond dissociation energy of "E-H" bond of the "$\mathrm{H}_{2} \mathrm{E}$ " hydrides of group 16 elements (given below), follows order.

A. $\mathrm{O}$

B. $\mathrm{S}$

C. Se

D. $\mathrm{Te}$

Choose the correct from the options given below:
A
$\mathrm{A}>\mathrm{B}>\mathrm{C}>\mathrm{D}$
B
$\mathrm{D}>\mathrm{C}>\mathrm{B}>\mathrm{A}$
C
$\mathrm{B}>\mathrm{A}>\mathrm{C}>\mathrm{D}$
D
$\mathrm{A}>\mathrm{B}>\mathrm{D}>\mathrm{C}$
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