Chemistry · chapter PYQs

Classification of Elements and Periodicity in Properties, on the exam screen.

6 questions from NEET 2026, Re-NEET 2026, NEET 2020, 6 minutes, marked +4 / −1. See them with solutions.

Classification of Elements and Periodicity in Properties · PYQs

Candidate: You

Time Left

Q1/6

Question 1 · NEET 2026 · Q64 · +4 / −1
The correct order of increasing metallic character of Na, Be, P, Mg and Si is:
Answer and explanation
Answer: (1)
Metallic character decreases across a period (left to right) and increases down a group, and it is inversely related to electronegativity. Using Pauling electronegativities (Na 0.9 < Mg 1.2 < Be 1.5 < Si 1.8 < P 2.1), metallic character increases in the reverse order: P < Si < Be < Mg < Na.
Question 2 · NEET 2026 · Q88 · +4 / −1
Identify the incorrect statement from the following:
Answer and explanation
Answer: (1)
Cationic size decreases with increasing positive charge and across a period, so among Mg, $\mathrm{Mg}^{2+}$ , Al and $\mathrm{Al}^{3+}$ the largest species is neutral Mg and the smallest is $\mathrm{Al}^{3+}$ , not Al and $\mathrm{Mg}^{2+}$ ; hence statement (1) is incorrect and is the answer. The others are correct: element 107 is Unnilseptium, Li and Mg show a diagonal relationship, and Al in the given complex has oxidation state +3 with covalency 6.
Question 3 · Re-NEET 2026 · Q53 · +4 / −1
Among the following options, the correct trend in the electron gain enthalpy is
Answer and explanation
Answer: (3)
Chlorine, not fluorine, releases the most energy on gaining an electron. The 2p subshell of fluorine is so compact that the incoming electron meets strong inter-electronic repulsion, which offsets the favourable nuclear attraction; chlorine's larger 3p shell has no such penalty. Down the rest of the group the value falls with increasing size, giving Cl > F > Br > I. NCERT Class 11, Classification of Elements and Periodicity in Properties.
Question 4 · Re-NEET 2026 · Q70 · +4 / −1
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:
Answer and explanation
Answer: (1)
Oxygen is $[\mathrm{He}]2\mathrm{s}^2 2\mathrm{p}^4$ ; the fourth 2p electron must pair up in an already-occupied orbital and suffers extra repulsion, so it is comparatively easy to remove. Losing it gives $\mathrm{O}^{+}$ with the $2\mathrm{p}^3$ half-filled configuration, which is extra stable through exchange energy. That is precisely why oxygen's first ionization enthalpy dips below nitrogen's despite nitrogen having a smaller nuclear charge, and stays below fluorine's. R therefore explains A. NCERT Class 11, Classification of Elements and Periodicity in Properties.
Question 5 · NEET 2020 · Q114 · +4 / −1
Identify the incorrect match.
List I
List II
P) Unnilunium
I) Mendelevium
Q) Unniltrium
II) Lawrencium
R) Unnilhexium
III) Seaborgium
S) Unununnium
IV) Darmstadtium
Answer and explanation
Answer: (3)
Unnilunium, unniltrium and unnilhexium correctly correspond to elements 101, 103 and 106. The printed 'Unununnium' denotes element 111, whose official name is roentgenium, not darmstadtium; therefore S-IV is the incorrect match. Chapter: Classification of Elements and Periodicity in Properties.
Question 6 · NEET 2020 · Q116 · +4 / −1
Match each oxide with its nature and select the correct option.
List I
List II
P) CO
I) Basic
Q) BaO
II) Neutral
R) Al $_{2}$ O $_{3}$
III) Acidic
S) Cl $_{2}$ O $_{7}$
IV) Amphoteric
Answer and explanation
Answer: (1)
CO is neutral, BaO basic, Al $_{2}$ O $_{3}$ amphoteric and Cl $_{2}$ O $_{7}$ acidic. Thus P-II, Q-I, R-IV, S-III. Chapter: Classification of Elements and Periodicity in Properties.

List I	List II
P) Unnilunium	I) Mendelevium
Q) Unniltrium	II) Lawrencium
R) Unnilhexium	III) Seaborgium
S) Unununnium	IV) Darmstadtium

List I	List II
P) CO	I) Basic
Q) BaO	II) Neutral
R) Al $_{2}$ O $_{3}$	III) Acidic
S) Cl $_{2}$ O $_{7}$	IV) Amphoteric