Classification of Elements and Periodicity in Properties JEE Main PYQs (2020–2026)

Solved Classification of Elements and Periodicity in Properties PYQs

3 recent questions with answers. The full set of 136 is free to practise.

1. JEE Main 2026EasyPeriodic Trends: Ionization Enthalpy
   Q1

   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.

   • Alowest and lowest
   • Bhighest and lowest
   • Clowest and highest
   • Dhighest and highest

   Show answer & solution

   Correct answer: (C)

   The element on the far left of a period belongs to Group 1. These elements have only one electron in their outermost shell, so they lose this electron easily. Therefore, they have the lowest first ionisation enthalpy (IE).
   
   The element on the far right of a period, except noble gases, belongs to Group 17 (halogens). These atoms need just one electron to complete their outermost shell, so they strongly attract an extra electron. Hence, they have the most negative value of electron gain enthalpy ( $\Delta H_{eg}$ ).
2. JEE Main 2026EasyPeriodic Trends: Electronegativity & Valence
   Q2

   Given below are two statements:
   
   Statement I: The correct order of electronegativity of fluorine, oxygen and nitrogen is $F>O>N$.
   
   Statement II: The oxidation state of oxygen in ${OF}_2$ is +2 and in ${Na}_{2}O$ is -2.
   
   In the light of the above statements, choose the correct answer from the options given below

   • ABoth Statement I and Statement II are true
   • BBoth Statement I and Statement II are false
   • CStatement I is true but Statement II is false
   • DStatement I is false but Statement II is true

   Show answer & solution

   Correct answer: (A)

   Statement I:
   
   Electronegativity generally increases across a period from left to right.
   
   For the elements nitrogen, oxygen, and fluorine in the second period, the correct order is
   
   $$F>O>N$$
   
   So, Statement I is true.
   
   Statement II:
   
   Let us check the oxidation state of oxygen in both compounds.
   
   In ${OF}_2$
   
   Fluorine is the most electronegative element, so its oxidation state is always $-1$.
   
   Let the oxidation state of oxygen be $x$.
   
   Then,
   
   $$x+2(-1)=0$$
   
   $$x-2=0$$
   
   $$x=+2$$
   
   So, in ${OF}_2$, oxygen has oxidation state $+2$.
   
   In ${Na}_{2}O$
   
   Sodium has oxidation state $+1$.
   
   Let the oxidation state of oxygen be $x$.
   
   Then,
   
   $$2(+1)+x=0$$
   
   $$2+x=0$$
   
   $$x=-2$$
   
   So, in ${Na}_{2}O$, oxygen has oxidation state $-2$.
   
   Hence, Statement II is also true.
   
   Therefore, the correct answer is:
   
   $$\boxed{\text{Option A}}$$
   
   Both Statement I and Statement II are true.
3. JEE Main 2026EasyPeriodic Trends: Metallic and Non-metallic Nature
   Q3

   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.

   • A7 and 5
   • B6 and 7
   • C5 and 7
   • D5 and 6

   Show answer & solution

   Correct answer: (C)

   Metallic character increases down a group and decreases from left to right across a period (NCERT trend).
   
   Given elements:
   
   Period 2: $N,O,F$
   
   Period 3: $P,S,Cl$
   
   Most metallic element
   
   In period 3, metallic character is higher than in period 2, and within period 3 it decreases left to right:
   
   $$P>S>Cl$$
   
   So, $P$ is the most metallic among the given elements.
   
   Valence electrons in $P$ (Group 15) $=5$.
   
   Least metallic element
   
   Least metallic means most non-metallic, which is highest towards the top-right of the periodic table. Among the given, $F$ is the most non-metallic.
   
   Valence electrons in $F$ (Group 17) $=7$.
   
   Final Answer
   
   Number of valence electrons (most metallic, least metallic) $=(5,7)$.
   
   Option C: 5 and 7

Topic-wise question count

Where JEE Main has asked from Classification of Elements and Periodicity in Properties, most frequent first.

• Periodic Trends: Ionization Enthalpy41
• Periodic Trends: Atomic and Ionic Radii26
• Periodic Trends: Metallic and Non-metallic Nature25
• Modern Periodic Law & Periodic Table Classification16
• Periodic Trends: Electron Gain Enthalpy15
• Periodic Trends: Electronegativity & Valence10
• Diagonal Relationship & Anomalous Behaviour of Second Period Elements3

Year-wise Classification of Elements and Periodicity in Properties questions in JEE Main

Number of questions from this chapter in each year's paper(s).