JEE Main Pattern Practice Questions

Stop Reading. Start Scoring.

Sections 1 to 10 taught you the chapter. This section finds out whether you can use it under a clock, which is a completely different skill. There is no new theory here — just 30 questions built to the JEE Main pattern on Classification of Elements and Periodicity, and a marking scheme that punishes the thing students do most: guessing.

The rules of engagement

Key Point: Do not treat this as a reading exercise. Sit down with a blank sheet, a pen and a timer, and attempt all 30 questions in one unbroken sitting before you look at a single explanation.

The setup	What it is
Number of questions	30 (26 single-correct MCQs + 4 numerical-value-type questions, all given with four options here)
Marking scheme	$+4$ correct, $-1$ incorrect, $0$ unattempted
Maximum score	$30 \times 4 = 120$ marks
Minimum possible score	$30 \times (-1) = -30$ marks
Suggested time limit	35 minutes (JEE Main pace is about 1 minute per question)
Allowed	rough sheet, your own brain, and the data listed below
Not allowed	calculator, a printed periodic table, looking back at Sections 1 to 10

What you are allowed to assume

This chapter is data-heavy, so let us be clear about what you may carry into the drill from memory. Anything else a question needs, it gives you.

Data you may assume	Values
Pauling electronegativities, period 2	Li 1.0, Be 1.5, B 2.0, C 2.5, N 3.0, O 3.5, F 4.0
Pauling electronegativities, period 3 and group 1	Na 0.9, Mg 1.2, Al 1.5, Si 1.8, P 2.1, S 2.5, Cl 3.0; K 0.8, Rb 0.8, Cs 0.7
Atomic (covalent) radii, period 2 and 3	Li 152, Be 111, B 88, C 77, N 74, O 66, F 64 pm; Na 186, Mg 160, Al 143, Si 117, P 110, S 104, Cl 99 pm
Ionic radii	$\mathrm{Na^+}$ 95 pm, $\mathrm{F^-}$ 136 pm; $\mathrm{Li^+}$ 76, $\mathrm{Be^{2+}}$ 31, $\mathrm{Mg^{2+}}$ 72 pm
First ionization enthalpies, period 3 (kJ/mol)	Na 496, Mg 737, Al 577, Si 786, P 1012, S 1000, Cl 1251, Ar 1521
Group 13 first ionization enthalpies (kJ/mol)	B 801, Al 577, Ga 579, In 558, Tl 589
Electron gain enthalpies (kJ/mol)	F $-328$ , Cl $-349$ , Br $-325$ , I $-295$ ; O $-141$ , S $-200$ ; noble gases all positive
Ionization enthalpy of hydrogen	$1312\ \mathrm{kJ\ mol^{-1}}$ ( $= 13.6$ eV per atom); $1\ \mathrm{eV\ atom^{-1}} = 96.5\ \mathrm{kJ\ mol^{-1}}$
Slater's rules (main-group electron in an $ns$ or $np$ orbital)	each other electron in the same $(ns, np)$ group shields $0.35$ ; each electron in the $(n-1)$ shell shields $0.85$ ; each electron in $(n-2)$ or lower shields $1.00$ . For a $d$ or $f$ electron, others in the same group shield $0.35$ and every electron to the left shields $1.00$ . Use $Z_{\text{eff}} = Z - \sigma$ .

Unless a question says otherwise, "radius" means the covalent (or metallic) radius of the atom, all ionization enthalpies refer to isolated gaseous atoms or ions in their ground states, and the periodic table is the standard 18-group long form with the lanthanoids and actinoids in the f-block.

[Board] That $-1$ is not decoration. In the real paper, four wild guesses that produce one lucky hit earn you $4 - 3 = +1$ mark for four minutes of work — a terrible trade. But a question you have narrowed down to two options is worth attempting: on average that gives $\frac{4 - 1}{2} = +1.5$ marks per attempt. Ordering questions are exactly where this pays off — you can usually kill two options by checking a single anomaly (is B below Be? is Ga above Al? is Cl more negative than F?), and then the last two are a coin worth flipping. Leave blank only what you cannot narrow at all. For the numerical-value-type questions there is no negative marking in the actual JEE Main paper, but we keep $-1$ here on purpose — it forces you to check your arithmetic instead of typing the first number you get.

What this set covers

Topic map and self-scoring card for the 30-question JEE Main periodicity drill

Topic	Questions	How many
History, the periodic law, Moseley's work and IUPAC nomenclature	Q1 to Q3	3
Locating elements: period, group and block from $Z$ or configuration; counting elements	Q4 to Q7	4
Atomic and ionic radius orders, isoelectronic series, covalent radius from bond lengths, lanthanoid contraction	Q8 to Q12	5
Ionization enthalpy: orders with anomalies, successive values, group 13, ions, hydrogen-like species	Q13 to Q18	6
Electron gain enthalpy, second electron gain enthalpy, electronegativity and the Mulliken scale	Q19 to Q22	4
Effective nuclear charge, Slater's rules and shielding	Q23 to Q26	4
Valence and oxidation state, binary formulas, oxide and hydroxide character, reactivity orders	Q27 to Q30	4

That spread is deliberate — it mirrors how JEE Main actually samples this chapter. Ionization enthalpy, radius and the electron gain enthalpy/electronegativity block together account for 15 of the 30 questions, because in the real paper an "arrange in the correct order" question from one of those three topics appears almost every year, usually with one anomaly planted in it. $Z_{\text{eff}}$ gets four questions because it is the idea that explains all the others and JEE has started asking it directly. The difficulty mix is roughly 20% easy, 50% medium and 30% hard, so do not panic if a few feel brutal; they are meant to. Questions 18, 22, 23 and 26 are written in the numerical-value style: the answer is a number you must compute exactly, and the four options are there only so you can mark yourself.

Scoring Yourself Honestly

Mark your sheet with the real scheme — $+4$ , $-1$ , $0$ — and total it. Do not award yourself half marks for "I knew that one really" or "I only swapped Ga and Al". The number you get is the number that matters.

The bands

Your score (out of 120)	Verdict	What to do next
96 to 120	Exam ready. You are at 80% or above on a hard set.	Move on. Periodicity will not cost you marks. Revisit only the specific questions you missed.
72 to 95	Solid, but leaking marks.	These are almost always slips, not gaps — the N/O anomaly remembered but the Be/B one forgotten, $Z$ used where $Z^2$ was needed in a hydrogen-like ionization enthalpy, the 0.85 factor applied to the same shell instead of the inner one in Slater's rules. Redo every wrong question without looking at the explanation first.
44 to 71	Shaky. The ideas are there; the execution is not.	For each wrong answer, go back to the section it came from (use the topic map above) and re-work its solved examples before re-attempting.
Below 44	Start again.	Work through Sections 1 to 8 properly, then Section 9's solved examples and Section 10's JEE Corner, then come back. Re-attempting this set now teaches you nothing.

Read your own answer sheet

Before you touch the explanations, sort your mistakes into three piles. This is the most valuable ten minutes in the whole section.

Concept errors — you did not know that Ga is smaller than Al, or that chlorine's electron gain enthalpy is more negative than fluorine's, or that the second ionization enthalpy of Na is larger than that of Mg even though the first is smaller, or that group number for a d-block element is $ns + (n-1)d$ electrons. Fixable by revision, and quickly.
Execution errors — right method, wrong arithmetic: you counted seven electrons in the 3p group of chlorine instead of six "other" electrons for Slater's rules, forgot to square $Z$ in $\Delta_i H = 1312\,Z^2/n^2$ , added $-141$ and $+780$ and got the sign wrong, or lost the lanthanoids when counting to a $Z$ in period 6. Fixable by slowing down for four seconds at the last step.
Reading errors — you gave the largest ion when the question asked for the one that is not isoelectronic, arranged by ionization enthalpy when the question said electron gain enthalpy, ranked "increasing" when the options were written "decreasing", or answered for the ground state when the ion was in its first excited state. These are the cheapest marks in the paper to win back, and the ones students refuse to take seriously.

Key Point: A student who scores 76 with three concept errors is in far better shape than one who scores 76 with nine reading errors. The first has three things to learn. The second has a habit to break, and habits take longer.

[Board] Every explanation below is written as a full step-by-step solution, so this set doubles as revision material. Read the explanation even for the questions you got right — sometimes you got there the slow way, and the fast way ("group of a d-block element = $ns + (n-1)d$ ", "same shell 0.35, inner shell 0.85, everything else 1", "isoelectronic: more protons, smaller ion") is what you will need in the exam hall.

Classification of Elements and Periodicity in Properties