1
JEE Main 2021 (Online) 24th February Evening Slot
MCQ (Single Correct Answer)
+4
-1
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According to Bohr's atomic theory :

(A) Kinetic energy of electron is $$ \propto {{{Z^2}} \over {{n^2}}}$$.

(B) The product of velocity (v) of electron and principal quantum number (n), $$'vn' \propto {Z^2}$$.

(C) Frequency of revolution of electron in an orbit is $$ \propto {{{Z^3}} \over {{n^3}}}$$.

(D) Coulombic force of attraction on the electron is $$ \propto {{{Z^3}} \over {{n^4}}}$$.

Choose the most appropriate answer from the options given below :
A
(A), (C) and (D) only
B
(A) only
C
(C) only
D
(A) and (D) only
2
JEE Main 2020 (Online) 5th September Evening Slot
MCQ (Single Correct Answer)
+4
-1
The correct statement about probability density (except at infinite distance from nucleus) is :
A
It can be zero for 1s orbital
B
It can be zero for 3p orbital
C
It can never be zero for 2s orbital
D
It can negative for 2p orbital
3
JEE Main 2020 (Online) 5th September Morning Slot
MCQ (Single Correct Answer)
+4
-1
The difference between the radii of 3rd and 4th
orbits of Li2+ is R1 . The difference between the
radii of 3rd and 4th orbits of He+ is $$\Delta $$R2 .
Ratio $$\Delta $$R1 : $$\Delta $$R2 is :
A
8 : 3
B
3 : 2
C
2 : 3
D
3 : 8
4
JEE Main 2020 (Online) 5th September Morning Slot
MCQ (Single Correct Answer)
+4
-1
The correct electronic configuration and spin-only
magnetic moment (BM) of Gd3+ (Z = 64), respectively, are
A
[Xe]5f7 and 8.9
B
[Xe]4f7 and 7.9
C
[Xe]5f7 and 7.9
D
[Xe]4f7 and 8.9
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