Class 12 ChemistryChapter Notes
1 chapters · Definitions, key points, formulas & exam tips · Updated 2025-26
The Solid State
Key Definitions
Key Points to Remember
- →Types of solids: crystalline (definite shape, sharp melting point) and amorphous (irregular, no sharp MP).
- →Seven crystal systems and 14 Bravais lattices.
- →SC: CN=6, packing=52.4%. BCC: CN=8, packing=68%. FCC: CN=12, packing=74%.
- →HCP: packing efficiency 74% — most efficient.
- →Schottky defect: missing ions (density decreases). Frenkel defect: ion shifts to interstitial position (density unchanged).
- →n-type semiconductor: extra electrons (doped with group 15). p-type: electron holes (doped with group 13).
Formulas & Equations
Exam Tips
Know packing efficiencies and coordination numbers for SC, BCC, FCC.
Density formula: Z = number of atoms per unit cell — 1 for SC, 2 for BCC, 4 for FCC.
Distinguish between Schottky and Frenkel defects.
Frequently Asked Questions
Are these notes based on 2025-26 CBSE syllabus for Class 12 Chemistry?
Yes. All chapter notes here are based on the latest 2025-26 CBSE syllabus for Class 12 Chemistry. Deleted topics are clearly marked so you focus only on what will be tested in your board exam.
How to study Class 12 Chemistry notes effectively for board exams?
Read each chapter's notes once to build understanding. Then close the notes and try to recall every key point, definition, and formula from memory. Anything you miss is your weak area — revisit only those points. This active recall method takes less time and retains far more than re-reading.
What is the difference between NCERT notes and chapter summaries?
Chapter notes contain detailed definitions, key terms, formulas, and concept breakdowns — they're for learning and understanding. Chapter summaries are shorter paragraph-style overviews — they're for quick revision. Use notes when you're studying a chapter for the first time; use summaries the night before the exam.
Do I need to memorise formulas for Class 12 Chemistry CBSE board exam?
Yes. Formulas listed in these notes must be memorised precisely — CBSE doesn't give formula sheets during exams. Write each formula 5–10 times, then recall it without looking. In the exam, write the formula first, then substitute values — this helps you earn partial marks even if the final answer has a calculation error.