The p-Block Elements, Groups 13 to 18 — error notes

Aamirah Fathima · 4 November 2026 · 100 questions · 346 / 400 · target 240, danger 200

Score346/40086%

Target was240beaten by 106

EXCEPT stems4 of 6worst format again

Easy band86%below moderate 91%

A–R scaffold0 of 10printed, never used

346 out of 400 — 89 right, 10 wrong, one unanswered. The target on the cover was 240. She beat it by 106.

Two things have to be said straight away, and they pull in opposite directions.

The first is that the target was wrong. You asked yesterday why I had set it at 240 and I did not have a good answer. Here is the evidence: 240 was not a stretch, it was not even a floor, it was 106 marks below what she actually did on a paper built deliberately hard. A target that low teaches nothing. From here every target gets anchored to the Tamil Nadu government MBBS cutoff and worked backwards, not guessed from her last score.

The second is that this is a printed paper and her NEET is not. She scored 53% on the Chaitanya screen test and 86% here. Nothing in this paper tells us she would score 86% on a screen, and the gap between the two numbers is still the most important thing in the file.

What this paper does tell us is narrower and more useful: her method is now in place, and almost everything she lost she lost to three specific habits and one contradiction.

The marks

89 right, 10 wrong, 1 unanswered. 89×4 − 10 = 346. Of the 54 marks lost, 50 went to wrong answers and 4 to the single blank.

Band	Right	Of	Rate
Easy	13	15	86%
Moderate	41	45	91%
Hard	35	40	87%

The easy band is the weakest band on the paper, for the third paper running. On Work, Energy and Power it was 69% against a hard band of 75%. Here it is 86% against a moderate band of 91%. Both of her easy-band losses are below — neither of them is a gap in what she knows.

By section

Section	Right	Of	Lost
Group 13 — the boron family	14	16	Q6, Q11
Group 14 — the carbon family	16	16	—
Group 15 — the nitrogen family	17	20	Q38, Q48, Q50
Group 16 — the oxygen family	17	18	Q67
Group 17 — the halogens	15	18	Q72, Q73, Q88
Group 18 — the noble gases	10	12	Q89, Q91

By question format — this is where the answer is

Format	Right	Of	Rate
EXCEPT / negative stems	4	6	67%
Ordering and arranging	15	18	83%
Statement sets (four and five)	7	9	78%
Assertion–Reason	9	10	90%
Plain multiple choice	54	57	95%
Numerical and counting	15	16	94%
Questions with a figure	8	8	100%
Match the column	5	5	100%

Plain questions 95%, figures 100%, match tables 100%, numericals 94%. Every format she loses marks on is a format that asks her to hold several judgements at once before choosing — EXCEPT stems, orderings, statement sets. That is one problem wearing three hats, not three problems.

Where the 54 marks went

Family	Questions	Marks
EXCEPT stems — a true statement chosen	Q50, Q88	10
An order written backwards	Q6, Q73	10
A rule used, then denied	Q48	5
A counting question abandoned	Q67	4
Two options one character apart	Q89	5
The narrower set chosen	Q91	5
Genuine knowledge — halogen bond enthalpies	Q72	5
Genuine knowledge — P₄ geometry	Q38	5
Genuine knowledge — back bonding in BF₃	Q11	5

Of the 54 marks lost, 34 are habits and 15 are facts she does not yet know. That ratio has held on every paper since 1 November.

10 marks — and the third paper in a row

1. On an EXCEPT question she picks a statement because it is true

This is now beyond argument. On the four-chapter test in November she scored 7 of 8 on these and I wrote in the log that the family was settled. On Work, Energy and Power she scored 2 of 5. On this paper, 4 of 6 — the worst format on the paper, in a different subject again. Both losses are the identical mistake.

Q	The stem	Hers	The exception
Q50	Each of the following is true of dinitrogen, EXCEPT one.	(1) It forms nitrides with lithium and magnesium on heating	(4) It is prepared in the laboratory by heating ammonium nitrate
Q88	Each of the following is true of chlorine, EXCEPT one.	(4) It bleaches moist litmus permanently by oxidation	(1) With excess hot concentrated sodium hydroxide it gives sodium hypochlorite

Both of the statements she chose are completely true. Dinitrogen does form Li₃N and Mg₃N₂ on heating. Chlorine does bleach moist litmus permanently. She read each one, confirmed it, and ticked it — which is the right action for every other question on the paper and the wrong one here.

The two she needed are both single-word traps she would catch in any other format. Nitrogen in the lab comes from ammonium nitrite; ammonium nitrate gives nitrous oxide. Chlorine with cold dilute alkali gives hypochlorite, with hot concentrated alkali it gives chlorate. She knows both facts — option (3) of Q88 states the cold dilute case correctly and she left it alone.

The fix, unchanged for three papers: on any stem carrying EXCEPT, NOT, incorrect or wrong, put a small tick beside every option that is true, and then answer with the one that has no tick. Never choose an option on an EXCEPT question; eliminate down to it.

10 marks

2. Two orderings written exactly backwards

Three ordering questions lost out of eighteen. One is a real gap. The other two are the same list she knows, printed in reverse.

Q	What it asked	Hers	Right	What happened
Q6	Lewis acid strength of the boron trihalides	BI₃ < BBr₃ < BCl₃ < BF₃	BF₃ < BCl₃ < BBr₃ < BI₃	Character for character the reverse. She has the right sequence of four molecules and has written it from the wrong end.
Q73	“Arranged with the strongest oxidising agent first, the halogens come in the order”	I₂ > Br₂ > Cl₂ > F₂	F₂ > Cl₂ > Br₂ > I₂	Again the exact reverse. Fluorine is the strongest oxidising agent there is — she put it last. This is an easy-band question.
Q72	Bond dissociation enthalpy, largest first	Cl₂ > F₂ > Br₂ > I₂	Cl₂ > Br₂ > F₂ > I₂	This one is real. She knows Cl₂ is highest and that F₂ is anomalously low, but has not pushed F₂ below Br₂. A fact to learn, not a habit.

Q73 matters more than its five marks. It is an easy question about the single most famous ordering in the halogen chapter, and she reversed it. The stem said strongest first; she answered weakest first. This is the same mechanism as the 1 November paper, where she gave the fraction transferred when asked what was retained.

The fix: before looking at a single option on an ordering question, underline the direction word in the stem — largest, strongest, first, increasing — and write a small arrow beside it. Then check that the first item of the option she is about to tick is the one that word describes.

5 marks — and the most revealing thing on the paper

3. ⚠ She used a rule to answer one question and denied the same rule nine questions later

Question 39 printed the structure of phosphorous acid and asked for its basicity. She did something on that page I have not seen her do before and it is the best piece of work in the whole file: she circled both OH groups and drew a cross through the P–H bond. Then she answered dibasic, and she was right.

The rule she used, unstated but obvious from her own marks, is: the basicity of an oxoacid of phosphorus equals the number of P–OH groups it carries.

Question 48, nine questions later, listed five statements about the oxoacids of phosphorus. Statement E read, word for word: “The basicity of an oxoacid of phosphorus equals the number of P–OH groups it carries.” She drew a large cross through it.

Q	Her marks on the page	Result
Q39	Both OH groups circled, the P–H bond crossed out, basicity counted off the figure	Right
Q48	Statement E — the rule she had just used — crossed out as false	Wrong, −5

Everything else about her Q48 is excellent. She judged four of the five statements correctly, including the genuinely hard one (hypophosphorous acid is monobasic, not dibasic — she caught that). She was one judgement away from the mark, and the judgement she got wrong was the one she had already demonstrated she understood.

This is the same shape as the Chaitanya screen test, where her answer to Q125 contradicted her own answer to Q102 four questions earlier. It is not a knowledge problem. It is that each question is being answered in isolation, with no memory of the one before.

The fix: when a statement in a set states a general rule, test it against a specific case she can draw — and if she has drawn that case earlier in the same paper, she has already done the work.

A build finding, not a marks finding

4. ⚠ The Assertion–Reason scaffold was printed ten times and used zero times

After the Work, Energy and Power paper I built the prescription directly into the question paper. Every Assertion–Reason question on this paper carries a dashed box reading A true? ____ R true? ____ R explains A? ____, sitting between the Reason and the options, impossible to miss.

All ten boxes came back completely empty. Eight on the last paper, ten on this one: eighteen printed, eighteen untouched. The only red ink inside any of them is the upper arm of a tick passing through on its way to option (1).

Two things follow, and the second is more important than the first.

A printed prompt is not an intervention. She does not write where a box tells her to. I will stop putting the box on the paper; the habit has to be built on the rough sheet, which is where it has to live in 2027 anyway, because the computer-based exam gives her no question to write on.

And she does verify — in her own way, in her own place. On Q10 she drew a tick directly through the Reason text, confirming it where it stood, two centimetres above the empty box provided for exactly that purpose. She got Q10 right. On Q11 she drew a cross through the Assertion. She got Q11 wrong — not because she failed to check, but because the check returned the wrong answer.

And here is the part that matters. The full transcription of her red pen shows nine annotated questions, and every one of them is the prescribed technique for that format — carried out properly, just never inside the box.

Q	Format	What she drew
Q39	Figure	Both OH groups ringed, the P–H bond struck out	Right
Q45	Five statements	Tick after A, tick after B, cross through C, tick after D	Right
Q26	Four statements	Three small ticks, against A, B and C	Right
Q28	Match the column	A link line drawn from “Si (very pure)” to “semiconductor”	Right
Q49	Match the column	Two link lines — N₂O to laughing gas, N₂O₅ to the anhydride of nitric acid	Right
Q35	Ordering	Numerals written in the margin — a ringed 1 beside one step, a 4 beside another	Right
Q10	Assertion–Reason	A verification tick drawn straight through the Reason text	Right
Q11	Assertion–Reason	A cross at the end of the Assertion	Wrong
Q48	Five statements	A cross through statement E	Wrong

Seven of the nine are right, and the two that are not were marked correctly and judged wrongly — the technique did its job and handed her a wrong fact. Six weeks ago the instruction ‘mark the items before you choose’ existed only in my notes. It is now what she does on a figure, on a match table, on a statement set and on an ordering, unprompted. What is left to fix is not the method. It is the EXCEPT stems, where she has no mark to make, and the direction words.

That last point corrects something I wrote after the Work, Energy and Power paper. I said there that the two Assertion–Reason questions she annotated came out right and the two she left bare came out wrong, and I called it the cleanest causal result in the file. On this paper she annotated two and left eight bare, and scored 9 out of 10. The honest version is narrower: annotation does not make her right, it makes her slow down when she is unsure. When she knows the chemistry she does not need it, and when she is wrong about the chemistry it will not save her.

Three smaller losses worth naming

Q	What happened	Hers	Right
Q89	An easy-band question lost to one character. “Apart from helium, every noble gas has the outer configuration…” Options (2) and (3) differ by a single superscript. She took the one that is not a closed shell at all.	ns¹np⁶	ns²np⁶
Q91	The narrower set chosen. Which noble gases form compounds? She answered xenon alone. Krypton and radon both have reported compounds — this is the option-set family from the Chaitanya paper, in the too-few direction again.	xenon only	xenon, krypton and radon only
Q67	The one unanswered question, and it is a counting one. How many of four statements about sulphuric acid are correct? No tick, no working, nothing on the page. Three of the four are plain recall she has answered elsewhere; the fourth (“it is a monobasic acid”) is simply false.	left blank	Only three

Q67 is the seventh paper running on which the unanswered questions are the ones that ask her to count or compute. On the Chaitanya screen test ten of her thirteen blanks were of this kind. A counting question is not a hard question; it is a question that needs a sheet of paper, and she does not reach for one.

What went right — and most of this paper did

Group 14, the carbon family: 16 out of 16. Catenation, silicones, zeolites, fullerene ring counts, the whole section clean.
Match the column: 5 out of 5. With the four on the Chaitanya screen test and the three on Work, Energy and Power, that is twelve consecutive match questions without a single adjacent swap. This family cost her seven marks across four papers in October. It is fixed.
Every question with a figure: 8 out of 8. Diborane bridges, the graphite layers, XeF₂, the phosphorous acid structure. Her figure work is the strongest thing she does.
Numericals and counting: 15 out of 16. Oxidation states, bond pair and lone pair counts, the moles of nitric acid per mole of copper. The only loss is Q38, which is a geometry fact, not arithmetic.
Red working on nine questions, seven of them right — and every one of the nine is the right technique for its format. See the table in section 4; this is the clearest sign of progress in the file.
She flagged Q31 and Q34 in orange and returned to both. Both right. Flagging has now worked every single time she has used it, on every paper.
No collapse over the paper. First third 122 marks, middle third 117, last third 107. Compare the Chaitanya screen test, where she went 176, then 109, then 98. On paper she holds her pace.

Exam technique

The cover is blank again. No name, no date, no start time, no end time — the fourteenth paper in a row. I still cannot tell you whether she finished with twenty minutes to spare or ran out of road, and it is still the single most useful number I do not have. Two seconds of writing.

The response grid on the last page is untouched, also for the fourteenth time. The grid matters more each month: in 2027 she commits her answer in a different place from where she reads the question, and the grid is the only thing on a printed paper that rehearses that.

Her flag mark has changed shape again. Q31 carries an orange underline, Q34 an orange ring. On Work, Energy and Power it was a star and an underline; before that a blue ring; before that an orange ring. Five papers, five different marks. The orange pen is the only constant — and both flags on this paper were cleared and both were right.

What to carry into the next paper

On EXCEPT questions, tick the true ones first. 10 marks here, 15 on the last paper.
Never choose an option on an EXCEPT question. Tick every statement that is true and answer with the one left bare. Both losses this time were true statements she had confirmed and then ticked.
Underline the direction word before reading the options. 10 marks.
Largest, strongest, first, increasing. Two of her three ordering losses are the correct list written from the wrong end, and one of them was an easy question about fluorine.
When a statement states a rule, test it on a case she can draw. 5 marks.
She crossed out the basicity rule on Q48 having used it correctly on Q39. The drawing was already on the page.
Any question that asks ‘how many’ gets written out. 4 marks, and the seventh paper running.
A, B, C, D down the margin with T or F against each. Q67 was three statements she knows and one that is plainly false, and it came back blank.
Write the start and end time on the cover.
Fourteen papers. Until that is there I am guessing about pace.

89 right, 10 wrong, 1 unanswered: 89×4 − 10 = 346. Every lost mark is accounted for — 10×5 = 50 to wrong answers and 1×4 = 4 to the blank, totalling 54 from 400. The script was read by the geometric tick-finder and independently by eye against the page images; every wrong answer, the blank, both flag marks and all ten Assertion–Reason scaffold boxes were re-checked individually at 300 dpi. All three readings agree on all 100 answers, the blank included. This paper was built to the Chaitanya chemistry envelope measured on 2 November: bands 15 easy / 45 moderate / 40 hard, with nine option-set questions mixed in both directions, five match tables, six negative stems and eighteen orderings.