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Revision Notes

Elements of Groups 16, 17 and 18

Maharashtra Board · Class 12 · Chemistry

Quick revision notes for Elements of Groups 16, 17 and 18 — Maharashtra Board Class 12 Chemistry. Key concepts, formulas, and definitions for last-minute revision.

45 questions25 flashcards5 concepts

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Key Topics to Revise

1

Electronic Configuration and General Properties

  • Group 16: ns²np⁴ (need 2 electrons to complete octet)
  • Group 17: ns²np⁵ (need 1 electron to complete octet)
  • Group 18: ns²np⁶ (complete octet, chemically inert)
2

Anomalous Behavior of First Elements

  • Oxygen anomalies: diatomic (O₂), paramagnetic, shows -2, -1, +2 oxidation states only
  • H₂O is liquid due to hydrogen bonding while other hydrides are gases
  • Fluorine anomalies: highest electronegativity, shows only -1 oxidation state
3

Chemical Reactivity and Oxidation States

  • Group 16: Common oxidation states -2, +2, +4, +6 (except O: -2, -1, +2)
  • Group 17: F shows -1 only; others show -1, +1, +3, +5, +7
  • Group 18: Generally zero valent; Xe shows +2, +4, +6, +8
4

Allotropy and Important Compounds

  • Sulfur allotropes: Rhombic (α-S₈, stable <369K) and Monoclinic (β-S₈, stable >369K)
  • Both have S₈ puckered ring structure
  • Ozone (O₃): Angular molecule, powerful oxidizing agent, protects from UV rays

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Full Notes

Key Concepts

Group 16 has ns²np⁴ configurationOxygen is diatomic (O₂) and paramagneticIndustrial preparation involvesPrepared by silent electric discharge throughHalogens (X₂) show decreasing reactivity down

Frequently Asked Questions

What are the important topics in Elements of Groups 16, 17 and 18 for Maharashtra Board Class 12 Chemistry?
Elements of Groups 16, 17 and 18 covers several key topics that are frequently asked in Maharashtra Board Class 12 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Elements of Groups 16, 17 and 18 — Maharashtra Board Class 12 Chemistry?
Understand the core concepts first, then work through the 45 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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