Classification & Periodicity

20 JEE Main questions · Chemistry

ChemistryJEE Main 21 Jan 2026, Shift 1·Q2·MCQ·Easy–moderate
Open
Periodic trends in properties
Which of the following represents the correct trend for the mentioned property ?
- (A)F $>$ P $>$ S $>$ B – First Ionization Energy
- (B)Cl $>$ F $>$ S $>$ P – Electron Affinity
- (C)K $>$ Al $>$ Mg $>$ B – Metallic character
- (D) $\ce{K2O}$ $>$ $\ce{Na2O}$ $>$ $\ce{MgO}$ $>$ $\ce{Al2O3}$ – Basic character
Choose the correct answer from the option given below.
1. (1)A, B and D only
2. (2)A, B, C and D
3. (3)A and B only
4. (4)B and C only
We corrected a printing error in the original paper
Source printed “Frist Ionization Energy”.
ChemistryJEE Main 21 Jan 2026, Shift 2·Q10·MCQ·Easy–moderate
Open
Atomic radii and electron gain enthalpy
Given below are two statements:
Statement-I: The correct order in terms of atomic/ionic radii is Al $>$ Mg $>$ $\ce{Mg^{2+}}$ $>$ $\ce{Al^{3+}}$ .
Statement-II: The correct order in terms of the magnitude of electron gain enthalpy is Cl $>$ Br $>$ S $>$ O.
In the light of the above statements, choose the correct answer from the options given below:
1. (1)Both Statement I and Statement II are false
2. (2)Statement I is false but Statement II is true
3. (3)Statement I is true but Statement II is false
4. (4)Both Statement I and Statement II are true
ChemistryJEE Main 22 Jan 2026, Shift 1·Q5·MCQ·Easy–moderate
Open
First ionisation enthalpy values
A ‘p'-block element (E) and hydrogen form a binary cation $\ce{(EH_x)^+}$ , while $\ce{EH3}$ on treatment with $\ce{K2HgI4}$ in alkaline medium gives a precipitate of basic mercury(II)amido-iodine. Given below are first ionisation enthalpy values (kJ mol $^{-1}$ ) for first element each from group 13, 14, 15 and 16. Identify the correct first ionisation enthalpy value for element E.
1. (1)1312
2. (2)1086
3. (3)1402
4. (4)801
ChemistryJEE Main 22 Jan 2026, Shift 2·Q12·MCQ·Easy–moderate
Open
Ionisation and electron gain enthalpy
Given below are two statements :
Statement-I : C $<$ O $<$ N $<$ F is the correct order in terms of first ionization enthalpy values.
Statement-II : S $>$ Se $>$ Te $>$ Po $>$ O is the correct order in terms of the magnitude of electron gain enthalpy values.
In the light of the above statements, choose the correct answer from the options given below :
1. (1)Statement-I is false but Statement-II is true
2. (2)Both Statement-I and Statement-II are true.
3. (3)Both Statement-I and Statement-II are false.
4. (4)Statement-I is true but Statement-II is false.
ChemistryJEE Main 23 Jan 2026, Shift 1·Q3·MCQ·Easy
Open
Ionization enthalpy trend
The correct trend in the first ionization enthalpies of the elements in the 3 $^\text{rd}$ period of periodic table is:
1. (1)Al $<$ Si $<$ S $<$ P $<$ Cl
2. (2)Al $<$ S $<$ P $<$ Si $<$ Cl
3. (3)Si $<$ S $<$ Al $<$ P $<$ Cl
4. (4)S $<$ Si $<$ Al $<$ P $<$ Cl
ChemistryJEE Main 23 Jan 2026, Shift 2·Q6·MCQ·Easy–moderate
Open
Electronegativity trend in group 15
Elements X and Y belong to Group 15. The difference between the electronegativity values of ‘X' and phosphorus is higher than that of the difference between phosphorus and ‘Y'. ‘X' & ‘Y' are respectively
1. (1)N & As
2. (2)As & Bi
3. (3)Bi & N
4. (4)As & Sb
ChemistryJEE Main 23 Jan 2026, Shift 2·Q9·MCQ·Easy–moderate
Open
Ionisation enthalpy and ionic radius
Given below are two statements :
Statement I : The second ionisation enthalpy of Na is larger than the corresponding ionisation enthalpy of Mg.
Statement II : The ionic radius of $\ce{O^{2-}}$ is larger than that of $\ce{F-}$ .
In the light of the above statements, choose the correct answer from the options given below.
1. (1)Both statement I and statement II are true
2. (2)Both statement I and statement II are false
3. (3)Statement I is false but statement II is true
4. (4)Statement I is true but statement II is false
ChemistryJEE Main 24 Jan 2026, Shift 1·Q20·MCQ·Easy
Open
Metallic character atomic ionic radius
Given below are two statements :
Statement I : K $>$ Mg $>$ Al $>$ B is the correct order in terms of metallic character.
Statement II : Atomic radius is always greater than the ionic radius for any element.
In the light of the above statements, choose the correct answer from the options given below
1. (1)Both Statement I and Statement II are true
2. (2)Both Statement I and Statement II are false
3. (3)Statement I is false but Statement II is true
4. (4)Statement I is true but Statement II is false
ChemistryJEE Main 24 Jan 2026, Shift 2·Q11·MCQ·Moderate
Open
Second ionisation enthalpy trend
The correct order of C, N, O and F in terms of second ionisation potential is
1. (1)F $<$ N $<$ C $<$ O
2. (2)C $<$ O $<$ N $<$ F
3. (3)C $<$ N $<$ F $<$ O
4. (4)C $<$ F $<$ N $<$ O
We corrected a printing error in the original paper
Answer corrected; the source key is (2) — second ionisation enthalpies are C 2353, N 2856, F 3374, O 3388 kJ mol $^{-1}$ ( $\ce{O+}$ loses an electron from the stable half-filled 2p $^3$ ), so C $<$ N $<$ F $<$ O, option (3); the source's own solution also gives O $>$ F $>$ N $>$ C.
ChemistryJEE Main 28 Jan 2026, Shift 1·Q19·MCQ·Easy
Open
Atomic radius periodic trend
In period 4 of the periodic table, the elements with highest and lowest atomic radii are respectively.
1. (1)Na & Cl
2. (2)K & Se
3. (3)K & Br
4. (4)Rb & Br
ChemistryJEE Main 28 Jan 2026, Shift 2·Q3·MCQ·Easy
Open
Metallic character and valence electrons
Consider the elements N, P, O, S, Cl and F. The number of valence electrons present in the elements with most and least metallic character from the above list is respectively.
1. (1)7 and 5
2. (2)5 and 6
3. (3)5 and 7
4. (4)6 and 7
ChemistryJEE Main 2 Apr 2026, Shift 1·Q9·MCQ·Easy–moderate
Open
Ionisation enthalpy trends
Given below are two statements :
Statement (I) : The first ionisation enthalpy of the elements Na, Mg, Cl and Ar follows the order
Na $>$ Mg $>$ Cl $>$ Ar
Statement (II) : Among Ca, Al, Fe and B, the third ionisation enthalpy is very high for Ca.
In the light of the above statements, choose the correct answer from the options given below :
1. (1)Both Statement I and Statement II are true
2. (2)Both Statement I and Statement II are false
3. (3)Statement I is true but Statement II is false
4. (4)Statement I is false but Statement II is true
ChemistryJEE Main 2 Apr 2026, Shift 2·Q8·MCQ·Easy–moderate
Open
Acidic basic amphoteric neutral oxides
The correct set that contains all kinds (basic, acidic, amphoteric and neutral) of oxides is :
1. (1) $\ce{Na2O}$ , $\ce{K2O}$ , $\ce{Al2O3}$ and $\ce{As2O3}$
2. (2) $\ce{Al2O3}$ , $\ce{As2O3}$ , CO and NO
3. (3) $\ce{K2O}$ , $\ce{Cl2O7}$ , $\ce{As2O3}$ and NO
4. (4) $\ce{Na2O}$ , $\ce{N2O}$ , $\ce{Al2O3}$ and CO
ChemistryJEE Main 2 Apr 2026, Shift 2·Q9·MCQ·Easy–moderate
Open
Ionization enthalpy trends groups 13-14
Given below are two statements :
Statement-I : The second ionization enthalpy of B, Al and Ga is in the order of B $>$ Al $>$ Ga.
Statement-II : The correct order in terms of first ionization enthalpy is Si $<$ Ge $<$ Pb $<$ Sn.
In the light of the above statements, choose the correct answer from the options given below :
1. (1)Both Statement-I and Statement-II are true.
2. (2)Both Statement-I and Statement-II are false.
3. (3)Statement-I is true but Statement-II is false.
4. (4)Statement-I is false but Statement-II is true.
ChemistryJEE Main 4 Apr 2026, Shift 2·Q7·MCQ·Easy
Open
Successive ionisation enthalpy
The 1 $^\mathrm{st}$ ionization enthalpy for Mg is $+737$ kJ/mol. The most probable estimated value of the 2 $^\mathrm{nd}$ ionization enthalpy of Mg is .
1. (1) $-906$ kJ/mol
2. (2) $-856$ kJ/mol
3. (3) $+1450$ kJ/mol
4. (4) $+590$ kJ/mol
ChemistryJEE Main 5 Apr 2026, Shift 1·Q8·MCQ·Easy
Open
Electronegativity and oxidation states
Statement I : The correct order of electronegativity of fluorine, oxygen and nitrogen is F $>$ O $>$ N.
Statement II : The oxidation state of oxygen in $\ce{OF2}$ is $+2$ and in $\ce{Na2O}$ is $-2$ .
In the light of the above statements, choose the correct answer from the options given below
1. (1)Both Statement I and Statement II are true
2. (2)Both Statement I and Statement II are false
3. (3)Statement I is true but Statement II is false
4. (4)Statement I is false but Statement II is true
We corrected a printing error in the original paper
Source printed “of fluorine, oxygen nitrogen”.
ChemistryJEE Main 5 Apr 2026, Shift 2·Q8·MCQ·Easy–moderate
Open
Nature of oxides
Given below are two statements :
Statement-I : The number of pairs among [ $\ce{Al2O3}$ , $\ce{Cr2O3}$ ], [ $\ce{Cl2O7}$ , $\ce{Mn2O7}$ ], [ $\ce{Na2O}$ , $\ce{V2O3}$ ] and [ $\ce{CO}$ , $\ce{N2O}$ ] that contain oxides of same nature (acidic, basic, neutral or amphoteric) is 4.
Statement-II : Among $\ce{Na2O}$ , $\ce{Al2O3}$ , $\ce{CO}$ and $\ce{Cl2O7}$ , the most basic and acidic oxides are $\ce{Na2O}$ and $\ce{Cl2O7}$ , respectively.
In the light of the above statements, choose the correct answer from the options given below :
1. (1)Both Statement-I and Statement-II are true.
2. (2)Both Statement-I and Statement-II are false.
3. (3)Statement-I is true but Statement-II is false.
4. (4)Statement-I is false but Statement-II is true.
ChemistryJEE Main 6 Apr 2026, Shift 1·Q21·Numerical·Easy–moderate
Open
Ionisation enthalpy energy calculation
First and second ionization enthalpies of lithium are 520 kJ mol $^{-1}$ and 7297 kJ mol $^{-1}$ respectively. Energy required to convert 3.5 mg lithium (g) into $\ce{Li^2+}$ (g) [ $\ce{Li(g) -> Li^2+(g)}$ ] is kJ. (nearest integer)
[Molar mass of Li = 7 g mol $^{-1}$ ]
We corrected a printing error in the original paper
Source printed the unit of the answer as “kJ mol $^{-1}$ ”; the energy for 3.5 mg of lithium is in kJ.
ChemistryJEE Main 6 Apr 2026, Shift 2·Q8·MCQ·Easy
Open
Ionisation and electron gain enthalpy
In a period, the first ionisation enthalpy of the element at extreme left and the negative electron gain enthalpy of the extreme right element, except noble gases, are respectively.
1. (1)lowest and lowest
2. (2)highest and lowest
3. (3)lowest and highest
4. (4)highest and highest
ChemistryJEE Main 8 Apr 2026, Shift 2·Q8·MCQ·Easy–moderate
Open
Ionization enthalpy trends
Match List-I with List-II.
List-I List-II
Electronic configuration of neutral atom (where n = 2) 1 $^\mathrm{st}$ Ionization Energy (kJ mol $^{-1}$ )
A. ns $^2$ I. 2080
B. ns $^2$ np $^1$ II. 899
C. ns $^2$ np $^3$ III. 800
D. ns $^2$ np $^6$ IV. 1402
Choose the correct answer from the options given below :
1. (1)A-II, B-III, C-IV, D-I
2. (2)A-IV, B-III, C-II, D-I
3. (3)A-III, B-II, C-IV, D-I
4. (4)A-III, B-II, C-I, D-IV

	List-I		List-II
	Electronic configuration of neutral atom (where n = 2)		1 $^\mathrm{st}$ Ionization Energy (kJ mol $^{-1}$ )
A.	ns $^2$	I.	2080
B.	ns $^2$ np $^1$	II.	899
C.	ns $^2$ np $^3$	III.	800
D.	ns $^2$ np $^6$	IV.	1402