Classification of Elements and Periodicity in PropertiesNEET MCQs with solutions
Classification of Elements and Periodicity covers the modern periodic table, periodic trends (atomic radius, ionisation enthalpy, electron gain enthalpy, electronegativity) and anomalous properties. NEET tests trend comparisons across periods and groups, exceptions to trends, and diagonal relationships.
- Class
- 11 Chemistry
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- 24 questions
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- 551 questions
- ELITE questions
- 234
- NCERT topics
- 14
Practise 24 questions
Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1Important PYQ Mixed Concepts
Which order of first ionisation enthalpies for Na, Mg, Al and Si is correct?
Not quite — the answer is C.
Across Period 3, first ionisation enthalpy generally increases, but Al (3p¹) is lower than Mg (3s²) because Mg has a stable filled 3s² subshell. The correct order is Na < Al < Mg < Si.
Q2Ionization Enthalpy
Which of the following correctly explains why ionization enthalpy generally increases across a period?
Not quite — the answer is B.
Across a period, electrons are added to the same shell while nuclear charge increases, raising Zeff and strengthening the hold on valence electrons. Option C is incorrect — shielding stays nearly constant across a period.
Q3Grand Test
Which statement regarding the modern periodic law is correct?
Not quite — the answer is B.
The modern periodic law states that physical and chemical properties of elements are periodic functions of their atomic numbers. Atomic number determines electronic configuration, which governs all periodic behaviour.
Q4Mixed Revision
Which statement correctly represents the modern periodic law?
Not quite — the answer is C.
The modern periodic law, proposed by Moseley, states that the physical and chemical properties of elements are periodic functions of their atomic numbers, not atomic masses.
Q5Electronic Configurations of Elements and Periodicity
Which quantum number directly corresponds to the period number of an element in the modern periodic table?
Not quite — the answer is B.
Period number equals the principal quantum number (n) of the outermost (valence) shell. Azimuthal quantum number l determines subshell type (s/p/d/f), not the period.
Q6Modern Periodic Law & Long Form of Periodic Table
Which of the following is the correct basis of modern periodic classification?
Not quite — the answer is B.
Modern Periodic Law (Moseley) states that properties are periodic functions of atomic number, not atomic mass. Mass number and neutron number are distractors — neither governs periodicity.
Q7Electron Gain Enthalpy
Which of the following correctly explains why electron gain enthalpy becomes less negative going down a group?
Not quite — the answer is A.
As atomic size increases down a group, the incoming electron is farther from the nucleus and experiences weaker attraction, so less energy is released and EGE becomes less negative. Nuclear charge actually increases down a group (B), so that factor alone would predict more negative EGE — size and shielding override it. Option D is factually wrong — shielding increases down a group.
Q8Atomic Radii
Which type of radius is defined as half the distance between nuclei of two bonded atoms of the same element?
Not quite — the answer is B.
Covalent radius is defined as half the internuclear distance between two identical bonded atoms. van der Waals radius applies to non-bonded atoms; metallic radius to atoms in crystal lattice.
Q9Ionic Radii
Which of the following species is largest in size?
Not quite — the answer is D.
Cl⁻ has gained an electron, increasing electron-electron repulsion while nuclear charge remains the same, expanding the electron cloud beyond neutral Cl. Cations like Na⁺ are always smaller than their parent atoms.
Q10Diagonal Relationship
Which of the following correctly explains why diagonal elements resemble each other despite being in different groups and periods?
Not quite — the answer is C.
Moving down a group increases atomic size; moving across a period decreases it. These two opposing trends nearly cancel for diagonal elements, resulting in similar ionic radii and charge density. It is this charge/size similarity — not group membership or configuration — that drives the diagonal relationship.
Q11Electronegativity
Which of the following elements has the highest electronegativity on the Pauling scale?
Not quite — the answer is B.
Fluorine has the highest electronegativity (4.0 on Pauling scale) due to its smallest atomic size and high effective nuclear charge, which together create the strongest pull on bonding electrons. Oxygen (A) is second highest (3.5) — a common confusion point. Cl (D) has the highest EGE but not the highest EN — this distinction is a frequent NEET trap.
Q12Periodic Trends in Chemical Properties
Which of the following correctly explains why metallic character decreases across a period?
Not quite — the answer is B.
As effective nuclear charge increases across a period, the outermost electrons are held more tightly by the nucleus, making electron loss progressively harder and reducing metallic character. Atomic radius decreases (not increases) across a period. Shielding remains nearly constant across a period — it increases down a group.
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Get RankUp on Google PlayQ13Anomalous Properties of First Element of Each Group
Which of the following best explains why the first element of a group behaves anomalously compared to the rest?
Not quite — the answer is B.
First elements have the smallest atomic radius and highest electronegativity in their group, giving them uniquely high charge density and polarising power. This causes covalent character, distinct bond types, and diagonal relationships not seen in heavier congeners. Size and electronegativity together — not any single factor — drive the anomaly.
Q14Nomenclature of Elements with Atomic Number > 100
Which root represents the digit 0 in the IUPAC systematic nomenclature?
Not quite — the answer is B.
The digit 0 is represented by "nil" in the IUPAC system. The 10 roots are: 0=nil, 1=un, 2=bi, 3=tri, 4=quad, 5=pent, 6=hex, 7=sept, 8=oct, 9=enn.
Q15Modern Periodic Law & Long Form of Periodic Table
Which of the following correctly explains why properties of elements are periodic functions of atomic number?
Not quite — the answer is B.
Electronic configuration repeats periodically as atomic number increases — elements with similar configurations show similar properties. Atomic mass (option C) does not increase uniformly due to isotopes, and neutrons (option D) show no periodic pattern.
Q16Modern Periodic Law & Long Form of Periodic Table
Which statement is INCORRECT regarding the modern periodic law?
Not quite — the answer is C.
Modern periodic table is based on atomic number, not atomic mass. Mendeleev used atomic mass, which caused anomalies (Ar/K, Co/Ni). Option A is correct — modern law did resolve these.
Q17Modern Periodic Law & Long Form of Periodic Table
Which of the following pairs of elements were incorrectly placed in Mendeleev's table but correctly placed in the modern periodic table?
Not quite — the answer is A.
Ar (atomic mass 39.9) was placed before K (39.1) by Mendeleev based on mass — this was an anomaly. The modern table based on atomic number (Ar=18, K=19) resolves it correctly. Na/Cl, C/Si, O/S had no such anomaly.
Q18Modern Periodic Law & Long Form of Periodic Table
Which scientist's X-ray experiments established atomic number as the fundamental property for periodic classification?
Not quite — the answer is A.
Moseley's X-ray spectroscopy experiments showed atomic number is the fundamental property, replacing atomic mass as the basis of classification. Mendeleev used atomic mass; Dobereiner and Newlands made earlier incomplete attempts.
Q19Modern Periodic Law & Long Form of Periodic Table
Which of the following correctly explains why atomic mass does NOT always increase with atomic number in the modern periodic table?
Not quite — the answer is C.
Isotopes of elements cause average atomic mass to deviate from a strict increasing order, as seen in pairs like Ar(39.9)–K(39.1) and Co(58.9)–Ni(58.7). Electrons (option B) contribute negligible mass.
Q20Modern Periodic Law & Long Form of Periodic Table
The total number of periods in the modern periodic table is:
Not quite — the answer is B.
The modern long form of the periodic table has exactly 7 periods, corresponding to the 7 energy levels (n=1 to n=7). Period 8 does not exist in the current table.
Q21Modern Periodic Law & Long Form of Periodic Table
Which period in the modern periodic table contains the maximum number of elements?
Not quite — the answer is C.
The 6th period contains 32 elements (Cs to Rn), including 10 d-block and 14 f-block (lanthanoid) elements. The 4th period (18 elements) is the next largest.
Q22Modern Periodic Law & Long Form of Periodic Table
Which block of elements is characterized by the progressive filling of p-orbitals?
Not quite — the answer is D.
p-block elements (Groups 13–18) have their last electron entering p-orbitals. s-block fills s-orbitals, d-block fills d-orbitals, and f-block fills f-orbitals.
Q23Modern Periodic Law & Long Form of Periodic Table
Hydrogen is placed separately or with Group 1 in the periodic table because it:
Not quite — the answer is A.
Hydrogen resembles alkali metals (loses 1e⁻, forms H⁺) and halogens (gains 1e⁻, forms H⁻, exists as diatomic H₂). This dual character makes its placement anomalous — no other element belongs to two groups.
Q24Modern Periodic Law & Long Form of Periodic Table
Helium (1s²) is placed in Group 18 despite being an s-block element. Which of the following BEST justifies this placement?
Not quite — the answer is B.
He (1s²) has a completely filled shell, giving it noble gas character identical to p-block Group 18 elements. Its placement is based on chemical behavior, not orbital type. Neon's configuration (2s²2p⁶) is different from He's.
ELITE question · AIR under 50 level
This chapter has 234 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appPeriodic Trends
Quick revision: most questions in this chapter test these facts.
| Property | Trend |
|---|---|
| Atomic radius | Decreases across period (↑ Zeff); increases down group (new shell) |
| Ionisation enthalpy | Increases across period; decreases down group; exceptions at half-filled/fully-filled |
| Electron gain enthalpy | Becomes more negative across period (halogens most); Cl > F (anomaly: small size of F) |
| Electronegativity | Increases across period; decreases down group; F is most electronegative |
| Metallic character | Decreases across period; increases down group |
| Diagonal relationship | Li~Mg, Be~Al, B~Si — similar charge/radius ratio gives similar properties |
What the app covers in this chapter
551 questions in total, each with a detailed explanation.
| Important PYQ Mixed Concepts | 99 |
| Ionization Enthalpy | 62 |
| Grand Test | 57 |
| Mixed Revision | 54 |
| Electronic Configurations of Elements and Periodicity | 41 |
| Modern Periodic Law & Long Form of Periodic Table | 40 |
| Electron Gain Enthalpy | 39 |
| Atomic Radii | 38 |
| Ionic Radii | 21 |
| Diagonal Relationship | 21 |
| Electronegativity | 20 |
| Periodic Trends in Chemical Properties | 20 |
| Anomalous Properties of First Element of Each Group | 20 |
| Nomenclature of Elements with Atomic Number > 100 | 19 |
Questions students ask
Is Periodic Table chapter important for NEET?
Yes — periodic trends and exceptions are tested every year. Questions compare ionisation enthalpies, atomic radii and electronegativities across periods and groups.
Which topics should I revise first?
Master all five periodic trends with their exceptions (why IE of N > O, why EA of Cl > F), diagonal relationships, and the anomalous properties of the first element of each group.
How many questions from this chapter are on RankUp?
The RankUp app has 551 questions on Classification of Elements and Periodicity in Properties, including 234 ELITE questions. Every question has a detailed explanation.
