What does Classification of Elements and Periodicity in Properties cover for NEET Chemistry?

7 lessons: Atomic Ionic Radii, Blocks of Periodic Table, Chemical Reactivity, Electron Gain Enthalpy, Ionization Enthalpy, Modern Periodic Law and Valence Oxidation States.

Classification of Elements and Periodicity in Properties

7 lessons

Topic index in NCERT order

7 of 7 lessons by the NCERT chapter they teach from, in book order. The page is the first printed page of your NCERT book the lesson cites; PYQs are the past NEET questions on that topic.

Class 11 Chemistry, Chapter 3

Atomic Ionic Radii

8 MCQs2 PYQsWorked example

Easy Recall (3)Direct Application (3)Calculation (1)Concept Trap (1)

Blocks of Periodic Table

8 MCQs1 PYQsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (2)

Chemical Reactivity

8 MCQs2 PYQsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (2)

Electron Gain Enthalpy

8 MCQs1 PYQsWorked example

Easy Recall (3)Direct Application (3)Calculation (1)Concept Trap (1)

Ionization Enthalpy

8 MCQs2 PYQs3 revision cardsWorked example

Easy Recall (3)Direct Application (3)Calculation (1)Concept Trap (1)

Modern Periodic Law

8 MCQs2 PYQsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (2)

Valence Oxidation States

8 MCQsWorked example

Easy Recall (3)Direct Application (3)Concept Trap (2)

Past-paper questions from this unit

10 questions from NEET 2020, 2022, 2023, 2024, 2025, 2026. Answers verified against NTA official keys.

By year in our set: 2020 (2) · 2022 (1) · 2023 (1) · 2024 (2) · 2025 (2) · 2026 (2)

Lesson: Electron Gain Enthalpy

NEET 2026

Among the following options, the correct trend in the electron gain enthalpy is

1F > Cl > Br > I

2Br > Cl > F > I

3Cl > F > Br > I

4I > Br > Cl > F

NTA Answer: Option 3(final)

Report an error · Every fix is public: corrections log

Lesson: Ionization Enthalpy

NEET 2026

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 O is lower than that of N and F. Reason R : The loss of an electron from O leads to stable half-filled p orbital. In light of the above statements, choose the most appropriate answer from the options given below:

1Both A and R are correct and R is the correct explanation of A.

2Both A and R are correct and R is NOT the correct explanation of A.

3A is correct but R is not correct.

4A is not correct but R is correct.

NTA Answer: Option 1(final)

Report an error · Every fix is public: corrections log

Lesson: Atomic Ionic Radii

NEET 2025

Which of the following statements are true? A. Unlike Ga that has a very high melting point, Cs has a very low melting point. B. On Pauling scale, the electronegativity values of N and Cl are not the same. C. Ar, K+, Cl–, Ca2+, and S2– are all isoelectronic species. D. The correct order of the first ionization enthalpies of Na, Mg, Al, and Si is Si >Al > Mg > Na. E. The atomic radius of Cs is greater than that of Li and Rb. Choose the correct answer from the options given below :

1A, C, and E only

2A, B, and E only

3C and E only

4C and D only

NTA Answer: Option 3(final)

Report an error · Every fix is public: corrections log

Lesson: Blocks of Periodic Table

NEET 2025

Which among the following electronic configurations belong to main group elements? A. [Ne]3s1 B. [Ar]3d34s2 C. [Kr]4d10 5s25p5 D. [Ar]3d104s1 E. [Rn]5f06d27s2 Choose the correct answer from the option given below :

1A, C and D only

2B and E only

3A and C only

4D and E only

NTA Answer: Option 3(final)

Report an error · Every fix is public: corrections log

Lesson: Ionization Enthalpy

NEET 2024Revised key

Arrange the following elements in increasing order of first ionization enthalpy: Li, Be, B, C, N Chose the correct answer from the options given below:

1Li < Be < B < C < N

2Li < B < Be < C < N

3Li < Be < C < B < N

4Li < Be < N < B < C

NTA Answer: Option 2(revised_final)

Report an error · Every fix is public: corrections log

Lesson: Chemical Reactivity

NEET 2024Revised key

Arrange the following elements in increasing order of electronegativity: N, O, F, C, Si Choose the correct answer from the options given below:

1Si < C < N < O < F

2Si < C < O < N < F

3O < F < N < C < Si

4F < O < N < C < Si

NTA Answer: Option 1(revised_final)

Report an error · Every fix is public: corrections log

Lesson: Atomic Ionic Radii

NEET 2023

The element expected to form largest ion to achieve the nearest noble gas configuration is

3Na

NTA Answer: Option 2(final)

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Lesson: Modern Periodic Law

NEET 2022

The IUPAC name of an element with atomic number 119 is

1ununoctium

2ununennium

3unnilennium

4unununnium

NTA Answer: Option 2(final)

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Lesson: Modern Periodic Law

NEET 2020

Identify the incorrect match. Name IUPAC Official Name (a) Unnilunium (i) Mendelevium (b) Unniltrium (ii) Lawrencium (c) Unnilhexium (iii) Seaborgium (d) Unununnium (iv) Darmstadtium

1(d), (iv)

2(a), (i)

3(b), (ii)

4(c), (iii)

NTA Answer: Option 1(final)

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Lesson: Chemical Reactivity

NEET 2020

Match the following : Oxide Nature (a) CO (i) Basic (b) BaO (ii) Neutral (c) Al2O3 (iii) Acidic (d) Cl2O7 (iv) Amphoteric Which of the following is correct option ? (a) (b) (c) (d)

1(iv) (iii) (ii) (i)

2(i) (ii) (iii) (iv)

3(ii) (i) (iv) (iii)

4(iii) (iv) (i) (ii)

NTA Answer: Option 3(final)

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Exam traps and common mistakes in this unit

Lesson: Atomic Ionic Radii

Trap

Inert gas atomic radius — van der Waals vs covalent

Category: Inorganic Exception

Student includes inert-gas radius in atomic-radius trends. But inert gases use van der Waals radius (much larger than covalent), making 'monotonic decrease across period' look broken.

When it triggers

Atomic radius comparison includes a noble gas or trends across period 2/3.

How to avoid

Compare like with like: covalent radii for non-noble gases. Noble gas radii are van der Waals (no covalent bond). Don't compare noble-gas radius directly to halogen.

Lesson: Ionization Enthalpy

Trap

IE anomaly: Be > B and N > O

Category: Inorganic Exception

Student expects monotonic increase in IE across period. Anomalies: Be(s²) > B(s²p¹); N(p³ half-filled) > O(p⁴).

When it triggers

Compare IE values across period 2 (Li, Be, B, C, N, O, F).

How to avoid

Be > B (s² stable; B's p¹ easier to remove). N > O (N has p³ half-filled stability; O loses one to attain p³). Memorise these two anomalies.

Lesson: Atomic Ionic Radii

Mistake

Compares noble-gas (van der Waals) radius to halogen (covalent) radius.

Root cause: concept gap

Correction

Don't compare different radius types. Noble gases use vdW radius (much larger); halogens use covalent radius. Compare like-with-like.

Lesson: Ionization Enthalpy

Mistake

Predicts monotonic IE increase across period (misses Be>B, N>O anomalies).

Root cause: concept gap

Correction

Be>B (s² stability); N>O (N's p³ half-filled stability). Memorise these two anomalies in period 2.

Formulas in this unit

Lesson: Ionization Enthalpy

Ionization energy of hydrogen-like atom

IE = \frac{13.6 Z ^{2}}{n ^{2}} eV

Energy required to ionize an electron from the n-th shell of hydrogen-like atom.

Symbol	Quantity	SI Unit
Z	nuclear charge	-
n	quantum number	-

Valid when

One-electron atom
Non-relativistic

NEET question patterns in this unit

Lesson: Atomic Ionic Radii

Periodic trends comparison — atomic/ionic radii, ionization energy, electron gain enthalpy, electronegativity.

Direct ApplicationMedium

Common distractors

swapped classes

Tempts surface-level recall.

Questions about this unit

What does Classification of Elements and Periodicity in Properties cover for NEET Chemistry?: 7 lessons: Atomic Ionic Radii, Blocks of Periodic Table, Chemical Reactivity, Electron Gain Enthalpy, Ionization Enthalpy, Modern Periodic Law and Valence Oxidation States.
How often has Classification of Elements and Periodicity in Properties come up in NEET past papers?: Our set of verified past papers has 10 questions from this unit, from NEET 2020, 2022, 2023, 2024, 2025 and 2026. Each is answered against the official NTA key.
Is the Classification of Elements and Periodicity in Properties material free?: Yes. All 7 lessons and 56 practice questions are free, with no login needed.