These 9th class chemistry chapter 8 notes are ExamPaperDesk’s own solved answers to the Chapter 8 exercise, Periodic Table and Periodicity, in both English medium and Urdu medium. Each PDF covers the chapter’s short-answer questions and constructed response questions, with clear answers you can revise from and follow when writing your own. Choose the English medium PDF (3 pages) or the Urdu medium PDF (3 pages) below.
For the rest of Chapter 8, you can read the Class 9 Chemistry Chapter 8 textbook PDF. The Class 9 Chemistry section of ExamPaperDesk brings notes, textbook PDFs, test papers, online papers, guess papers and past papers together, and you can already browse all Class 9 Chemistry notes and textbook PDFs.
Chapter 8 Notes English Medium PDF
Chapter 8 Notes Urdu Medium PDF
Chapter 8 Exercise: What You Are Expected to Be Able to Write
These solved answers cover the Chapter 8 exercise, Periodic Table and Periodicity. Reading a model answer is useful only as a check. The point of the exercise is that you can produce these yourself, in writing, under exam conditions. The chapter expects you to handle:
- Mendeleev periodic law and the modern periodic law, and the difference between them.
- The structure of the modern periodic table: periods, groups and blocks.
- Atomic radius and ionic radius, and how they vary across a period and down a group.
- Ionisation energy and electron affinity trends, with explanations.
- Electronegativity and its trend.
- Why elements in the same group have similar chemical properties.
The Statements That Must Be Exact
Chemistry is marked on precision of wording more than on length. For Periodic Table and Periodicity, these must be right:
- The modern periodic law arranges elements by increasing atomic number, not atomic mass as Mendeleev did.
- Atomic radius decreases across a period and increases down a group.
- Ionisation energy increases across a period and decreases down a group, which is the opposite of atomic radius.
Errors That Appear Year After Year
- Stating the modern periodic law in terms of atomic mass.
- Reversing the trend for ionisation energy and atomic radius.
- Confusing a group with a period.
How to Use Solved Answers Without Wasting Them
Attempt the question first with the solution covered, then uncover it and compare line by line. Mark the difference, not just the verdict: a missing condition, a wrong sign or a vague phrase is the thing to carry forward. Copying a model answer out neatly feels productive and teaches almost nothing, because recognition is not recall.
Frequently Asked Questions
How does atomic radius change across a period?
It decreases. The nuclear charge rises while electrons are added to the same shell, so the stronger pull draws the shell closer to the nucleus.
Are both mediums available?
The solved answers cover the chapter exercise and are free to download and print, with no sign-up needed.
Related Class 9 Chemistry Resources
Once you can write the answers unaided, sit the Chapter 8 test paper, a 36-mark bilingual practice paper with an MCQ answer key. Everything else for the subject is on the Class 9 Chemistry page, with the rest of the solved exercises under Class 9 Chemistry notes.