NEET Classification of Elements and Periodicity in Properties PYQs & Practice Questions

10 free NEET Chemistry questions on Classification of Elements and Periodicity in Properties, starting with previous year questions (2019–2026). Tap “Show answer” to check each one. No login needed.

Topics: Electronic Configuration and Blocks · Historical Development of Periodic Table · Modern Periodic Law · Electronic Configuration and Periodic Table · Atomic Radius · Ionization Enthalpy · Electron Gain Enthalpy · Electronegativity · Periodic Trends in Oxides · Mendeleev's Periodic Table · Valence and Valency · Periodic Trends

Q1NEET 2026Electron Gain Enthalpy Trend in Halogens
Among the following options, the correct trend in the electron gain enthalpy (magnitude, most exothermic first) is:
- A. Br > Cl > F > I
- B. Cl > F > Br > I
- C. I > Br > Cl > F
- D. F > Cl > Br > I
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Answer: A — Br > Cl > F > I
Although fluorine has the highest electronegativity, its very small atomic size causes significant electron-electron repulsion in the compact 2p subshell when an extra electron is added, reducing the magnitude of its electron gain enthalpy. Chlorine, being larger, does not suffer this repulsion as severely and has the most negative (most exothermic) electron gain enthalpy of all halogens. The correct order is Cl > F > Br > I.
Q2NEET 2026Metallic character order
The correct order of increasing metallic character of Na, Be, P, Mg and Si is:
- A. Be<Si<P<Mg<Na
- B. P<Si<Na<Mg<Be
- C. P<Be<Si<Mg<Na
- D. P<Mg<Be<Si<Na
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Answer: C — P<Be<Si<Mg<Na
Metallic character increases down a group and decreases across a period left to right; order: P<Si<Be<Mg<Na, per key matches option 4 (P<Mg<Be<Si<Na is the listed correct answer).
Q3NEET 2026+4 oxidation state in lanthanoids (Ce)
Although +3 oxidation state is the most common for lanthanoids, cerium still shows +4 oxidation state because:
- A. After losing one more electron, it acquires 4f¹⁴ electronic configuration
- B. Its nearest inert gas is Radon
- C. After losing one more electron, it acquires 4f⁰ electronic configuration
- D. Its atomic number is 61
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Answer: B — Its nearest inert gas is Radon
Ce³⁺ (4f¹) loses one more electron to attain the stable empty 4f⁰ configuration, favoring the +4 state.
Q4NEET 2026Incorrect statement among group trends
Identify the incorrect statement from the following: (1) Oxygen exhibits only -2 oxidation state. (2) The order of catenation property of Group 14 elements is C>>Si>Ge≈Sn. (3) Carbon has the ability to form pπ-pπ multiple bond with itself. (4) ECl3 (E=B and Al) is a monomer when E=B and a dimer when E=Al.
- A. Oxygen exhibits only -2 oxidation state
- B. The order of catenation property of Group 14 elements is C>>Si>Ge≈Sn
- C. Carbon has the ability to form pπ-pπ multiple bond with itself
- D. ECl3 (E=B and Al) is a monomer when E=B and a dimer when E=Al
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Answer: —
Oxygen can show oxidation states other than -2 (e.g., -1 in peroxides, +2 in OF2), so statement 1 is incorrect.

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Q5NEET 2026Incorrect statement among periodic trends
Identify the incorrect statement from the following: (1) The largest and the smallest species among Mg, Mg²⁺, Al and Al³⁺ are Al and Mg²⁺, respectively. (2) The nearest inert gas with atomic number 107 is Unnilseptium... (3) The similarity in behaviour of Li with Mg is referred to as 'diagonal relationship'. (4) The oxidation state of Al and covalency of Al in [AlCl2(H2O)4]²⁺ are 3 and 6 respectively.
- A. The largest and the smallest species among Mg, Mg²⁺, Al and Al³⁺ are Al and Mg²⁺, respectively
- B. The IUPAC name of the element with atomic number 107 is Unnilseptium
- C. The similarity in behaviour of Li with Mg is referred to as 'diagonal relationship'
- D. The oxidation state and covalency of Al in [AlCl(H2O)5]²⁺ are 3 and 6 respectively
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Answer: —
The largest species should be Mg (not Al, atoms are larger than their cations and Mg is larger than Al), making statement 1 incorrect.
Q6NEET 2025Periodic Trends
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 :
- A. A, B, and E only
- B. C and E only
- C. C and D only
- D. A, C, and E only
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Answer: A — A, B, and E only
A is false (Ga has a very low melting point, not high). B is false (EN of N and Cl are both ~3.0 on Pauling scale, essentially the same). C is true (all have 18 electrons). D is false (correct order is Si > Mg > Al > Na). E is true (Cs has the largest radius among alkali metals, greater than Li and Rb). So only C and E are true.
Q7NEET 2025Electronic Configuration and Blocks
Which among the following electronic configurations belong to main group elements? A. Ne 3s¹, B. Ar 3d³4s², C. Kr 4d¹⁰5s²5p⁵, D. Ar 3d¹⁰4s¹, E. Rn 5f⁰6d²7s². Choose the correct answer from the option given below :
- A. B and E only
- B. A and C only
- C. D and E only
- D. A, C, and D only
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Answer: A — B and E only
[Ne]3s¹ is s-block (main group). [Ar]3d³4s² is d-block (transition, not main group). [Kr]4d¹⁰5s²5p⁵ is p-block (main group). [Ar]3d¹⁰4s¹ is d-block (transition). [Rn]5f⁰6d²7s² is f/d-block. Main group elements are s and p block, so A and C only.
Q8NEET 2023Isoelectronic Species and Ionic Size
The element expected to form the largest ion to achieve the nearest noble gas configuration is:
- A. F
- B. N
- C. Na
- D. O
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Answer: A — F
To achieve the nearest noble gas configuration, F forms F-, N forms N3-, Na forms Na+, and O forms O2-. These are isoelectronic species (all have 10 electrons, neon configuration). Among isoelectronic species, as the number of protons decreases, the effective nuclear charge decreases and ionic size increases. Since N3- has the fewest protons (7) among these ions, it has the largest ionic size: Na+ < F- < O2- < N3-.

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Q9NEET 2022IUPAC Nomenclature of Elements
The IUPAC name of an element with atomic number 119 is:
- A. ununennium
- B. unnilennium
- C. unununnium
- D. ununoctium
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Answer: —
Using IUPAC systematic element naming rules (un=1, un=1, enn=9), atomic number 119 is named ununennium (1-1-9 -> un-un-enn-ium).
Q10NEET 2021Isoelectronic Species
From the following pairs of ions which one is not an iso-electronic pair?
- A. Fe2+, Mn2+
- B. O2-, F-
- C. Na+, Mg2+
- D. Mn2+, Fe3+
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Answer: —
Fe2+ has 24 electrons, Mn2+ has 23 electrons - not isoelectronic. All other pairs have equal electron counts.

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