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JEE Main 2021 (Online) 16th March Evening Shift
MCQ (Single Correct Answer)  +4  -1
Identify the elements X and Y using the ionisation energy values given below :

Ionization energy (kJ/mol)
1$${st}$$ 2$${nd}$$
X 495 4563
Y 731 1450
A
X = F; Y = Mg
B
X = Mg; Y = F
C
X = Na; Y = Mg
D
X = Mg; Y = Na
2
JEE Main 2021 (Online) 16th March Morning Shift
MCQ (Single Correct Answer)  +4  -1
Given below are two statement : one is labelled as Assertion A and the other is labelled as Reason R :

Assertion A : Size of Bk3+ ion is less than Np3+ ion.

Reason R : The above is a consequence of the lanthanoid contraction.

In the light of the above statements, choose the correct answer from the options given below :
A
Both A and B are true and R is the correct explanation of A
B
A is false but R is true
C
A is true but R is false
D
Both A and B are true but R is not the correct explanation of A
3
JEE Main 2021 (Online) 26th February Evening Shift
MCQ (Single Correct Answer)  +4  -1
The correct order of electron gain enthalpy is :
A
Te > Se > S > O
B
S > Se > Te > O
C
S > O > Se > Te
D
O > S > Se > Te
4
JEE Main 2021 (Online) 26th February Morning Shift
MCQ (Single Correct Answer)  +4  -1
Match List - I with List - II.

List I
Electronic configuration
List II
$${\Delta _i}H$$ in kJ $$mo{l^{ - 1}}$$
(a) $$1{s^2}2{s^2}$$ (i) 801
(b) $$1{s^2}2{s^2}2{p^4}$$ (ii) 899
(c) $$1{s^2}2{s^2}2{p^3}$$ (iii) 1314
(d) $$1{s^2}2{s^2}2{p^1}$$ (iv) 1402

Choose the most appropriate answer from the options given below :
A
(a) $$ \to $$ (i), (b) $$ \to $$ (iii), (c) $$ \to $$ (iv), (d) $$ \to $$ (iii)
B
(a) $$ \to $$ (iv), (b) $$ \to $$ (i), (c) $$ \to $$ (ii), (d) $$ \to $$ (iii)
C
(a) $$ \to $$ (ii), (b) $$ \to $$ (iii), (c) $$ \to $$ (iv), (d) $$ \to $$ (i)
D
(a) $$ \to $$ (i), (b) $$ \to $$ (iv), (c) $$ \to $$ (iii), (d) $$ \to $$ (ii)
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