Classification of Elements and Periodicity in Properties NEET PYQReal NEET & AIPMT 2005–2021 questions, year-tagged, with solutions
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Classification of Elements and Periodicity in Properties previous year questions
16 questions. Tap an option to check your answer.
Q1NEET 2021
From the following pairs of ions which one is not an iso-electronic pair ?
Not quite — the answer is D.
Fe²⁺ has 26 − 2 = 24 electrons, Mn²⁺ has 25 − 2 = 23, so they are not isoelectronic. O²⁻/F⁻ and Na⁺/Mg²⁺ each have 10 electrons, and Mn²⁺/Fe³⁺ each have 23.
Q2NEET 2020 · Q96
Identify the incorrect match. Name — IUPAC Official Name: (a) Unnilunium — (i) Mendelevium; (b) Unniltrium — (ii) Lawrencium; (c) Unnilhexium — (iii) Seaborgium; (d) Unununnium — (iv) Darmstadtium
Not quite — the answer is D.
Unununnium is element 111, which is roentgenium; darmstadtium is element 110 (ununnilium). Unnilunium (101) is mendelevium, unniltrium (103) is lawrencium and unnilhexium (106) is seaborgium, so those pairs are correct.
Q3NEET 2020 · Q131
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 ?
Not quite — the answer is B.
CO is a neutral oxide, BaO (from an alkaline earth metal) is basic, Al₂O₃ reacts with both acids and bases so it is amphoteric, and Cl₂O₇ is the anhydride of HClO₄ and strongly acidic. This follows the trend from basic metal oxides to acidic non-metal oxides.
Q4NEET 2019 · Q60
For the second period elements the correct increasing order of first ionisation enthalpy is:
Not quite — the answer is B.
IE generally rises across the period, but B < Be (Be has a filled 2s, B's 2p electron is easier to remove) and O < N (N has a stable half-filled 2p³; O's paired electron is repelled). Hence Li < B < Be < C < O < N < F < Ne.
Q5NEET 2018 · Q58
Which of the following oxides is most acidic in nature?
Not quite — the answer is B.
Down group 2 metallic character increases, so the oxides become more basic: BeO < MgO < CaO < BaO in basicity. BeO is amphoteric and thus the most acidic; BaO is the most basic.
Q6NEET 2017 · Q28
The element Z = 114 has been discovered recently. It will belong to which of the following family/group and electronic configuration?
Not quite — the answer is B.
After radon (Z = 86), 32 more electrons fill 7s² 5f¹⁴ 6d¹⁰ 7p², reaching Z = 86 + 2 + 14 + 10 + 2 = 114. A p² valence configuration places it in group 14, the carbon family (flerovium).
Q7AIPMT 2015
The species Ar, K⁺ and Ca²⁺ contain the same number of electrons. In which order do their radii increase?
Not quite — the answer is D.
All three have 18 electrons; the greater the nuclear charge (Ca 20 > K 19 > Ar 18), the more strongly the electrons are pulled in. So the radii increase Ca²⁺ < K⁺ < Ar.
Q8AIPMT 2012 Prelims
Identify the wrong statement in the following:
Not quite — the answer is B.
In an isoelectronic series, a larger positive charge pulls the same number of electrons more strongly and gives a smaller radius; so a smaller positive charge gives a larger, not smaller, radius. The other statements are correct: radius decreases across a period, increases down a group, and increases with greater negative charge.
Q9AIPMT 2011 Mains
What is the value of electron gain enthalpy of Na⁺ if IE₁ of Na = 5.1 eV?
Not quite — the answer is C.
Na⁺ + e⁻ → Na is exactly the reverse of Na → Na⁺ + e⁻ (IE₁ = 5.1 eV), so energy is released and ΔegH = −5.1 eV. +2.55 eV or ±10.2 eV come from wrongly halving or doubling the ionisation energy.
Q10AIPMT 2010 Mains · Q91
Among the elements Ca, Mg, P and Cl, the order of increasing atomic radii is
Not quite — the answer is B.
Across period 3 radius decreases (Mg > P > Cl), and down group 2 it increases (Ca > Mg). So the increasing order is Cl < P < Mg < Ca. Orders starting with Ca or Mg reverse the periodic trend.
Q11AIPMT 2010 Mains · Q97
Among the following which one has the highest cation to anion size ratio?
Not quite — the answer is B.
The ratio is largest when the cation is largest and the anion smallest: Cs⁺ is the biggest cation and F⁻ the smallest anion, so CsF (about 167/133 ≈ 1.26). CsI has a big cation but a much bigger anion, and LiF has the smallest cation.
Q12AIPMT 2010 Prelims · Q72
The correct order of the decreasing ionic radii among the following isoelectronic species is
Not quite — the answer is D.
All four ions have 18 electrons. Size falls as nuclear charge rises: S²⁻ (Z = 16) > Cl⁻ (17) > K⁺ (19) > Ca²⁺ (20). The orders putting cations first reverse this trend.
Q13AIPMT 2010 Prelims · Q79
Which of the following represents the correct order of increasing electron gain enthalpy with negative sign for the elements O, S, F and Cl?
Not quite — the answer is C.
Negative electron gain enthalpies: O ≈ 141, S ≈ 200, F ≈ 328, Cl ≈ 349 kJ/mol. O and F are less negative than S and Cl because their small size causes electron repulsion. So O < S < F < Cl.
Q14AIPMT 2009 Prelims · Q162
Amongst the elements with following electronic configurations, which one of them may have the highest ionization energy?
Not quite — the answer is D.
[Ne]3s²3p³ is phosphorus: a small period-3 atom with a stable half-filled 3p subshell, so it has the highest ionization energy here. [Ar]3d¹⁰4s²4p³ (arsenic) is also half-filled but larger, and the 3p¹ and 3p² atoms (Al, Si) lose electrons more easily.
Q15AIPMT 2005 Prelims · Q75
A nuclide of an alkaline earth metal undergoes radioactive decay by emission of three α-particles in succession. The group of the periodic table to which the resulting daughter element would belong is :
Not quite — the answer is A.
Each α-emission lowers Z by 2, so three α-particles lower Z by 6, i.e. six places back in the periodic table. From group 2 this goes to group 14 of the previous period (e.g. Ra, Z = 88 → Pb, Z = 82).
Q16AIPMT 2005 Prelims · Q96
Which one of the following arrangements represents the correct order of electron gain enthalpy (with negative sign) of the given atomic species ?
Not quite — the answer is B.
Cl has the most negative electron gain enthalpy. F and O are less negative than Cl and S because their small size causes strong electron–electron repulsion; also halogens exceed chalcogens. So O < S < F < Cl.
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