What Chapter 4 actually teaches
Class 9–10 Chemistry, Chapter 4 (pp. 59–81), is the periodic table chapter. It has three big ideas: how the elements came to be classified (including Mendeleev's periodic law), what groups and periods mean under the modern periodic law, and how properties change with position — atomic radius, ionisation energy, electronegativity, metallic character.
In one sentence, the chapter's core claim: the periodic table is a map, not a pile — know an element's address (group + period) and you can read off its electron structure and many of its properties. This page — and this site — exists to make that single sentence usable.
How the chapter shows up in exams
Looking at the recurring pattern, questions arrive along four paths: (1) explain-type — "explain the rules for placing an element in the periodic table"; (2) trend-dependent — "what happens to atomic radius moving left to right across a period, and why?"; (3) creative/সৃজনশীল — a stem gives an electron configuration or symbol and asks for group and period; (4) definitions — periodic law, group, period, valence electrons.
Notice that none of these reward pure memorisation — every one tests whether you can connect the rule to electron structure. So the study loop should match: learn the rule → apply it to a real element → practise writing it out.
How this site maps onto the chapter
Every element page on this site (iron, chlorine, …) carries the atomic number, mass, group, period, block, electron configuration (with the shell breakdown), characteristics, uses, history and six exam-style questions — chapter-level facts, element by element.
On top of that: group pages tell each family's story (Group 1 alkali metals, Group 18 noble gases), period pages walk a row of the table, and the Trends tool charts the four taught trends live. Quiz and Challenge are for sharpening before the exam.
The Bangla–English toggle earns its keep here: read in Bangla, then flip once — exam papers come in both registers, and holding both terminology sets is an advantage.
A 7-day study plan
Day 1 — read the chapter once, no notes. Day 2 — first 20 elements (this site's mnemonics page + quiz). Day 3 — placement rules; practise deriving position from configuration on the iron and calcium pages. Day 4 — the four trends in the Trends chart; write each "why" in your own words. Day 5 — Groups 1, 2, 17, 18 pages; make a family similarities/differences table. Day 6 — Quiz + 60-second Challenge. Day 7 — textbook exercises and past questions; loop back to element pages wherever you stall.
You asked
1Does this site match the NCTB textbook?
The core facts (atomic numbers, masses, configurations, groups/periods, family names, trends) follow the NCTB curriculum — but the site is a companion beside the book, not a replacement. Its exam questions are notes-based, so practising in the book's register remains the best final step.