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Periodic Table and Atomic Properties

Telangana Open School (TOSS) · Class 12 · Chemistry

Quick revision notes for Periodic Table and Atomic Properties — Telangana Open School (TOSS) Class 12 Chemistry. Key concepts, formulas, and definitions for last-minute revision.

43 questions35 flashcards5 concepts

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Key Topics to Revise

1

Historical Development of the Periodic Table

  • J.W. Dobereiner proposed the Law of Triads: the atomic weight of the middle element in a triad is approximately the average of the other two.
  • J.A.R. Newlands introduced the Law of Octaves, stating that every eighth element has similar properties, like musical notes.
  • Mendeleev's Periodic Table arranged elements by increasing atomic weight and left gaps for undiscovered elements, predicting their properties.
2

Modern Periodic Law and Table Structure

  • Modern Periodic Law: Properties of elements are periodic functions of their atomic numbers.
  • The long form of the periodic table has 18 groups and 7 periods.
  • Elements are classified into s-, p-, d-, and f-blocks based on the subshell in which the differentiating electron enters.
3

Electronic Configuration and Periodicity

  • The period number corresponds to the principal quantum number (n) of the valence shell.
  • Number of elements in a period depends on the number of orbitals being filled: 2 in period 1, 8 in periods 2–3, 18 in 4–5, 32 in 6–7.
  • s-Block: ns¹⁻²; p-Block: ns² np¹⁻⁶; d-Block: (n−1)d¹⁻¹⁰ ns⁰⁻²; f-Block: (n−2)f¹⁻¹⁴ (n−1)d⁰⁻¹ ns².
4

Periodic Trends in Atomic Properties

  • Atomic size decreases across a period (left to right) due to increasing nuclear charge pulling electrons closer.
  • Atomic size increases down a group due to addition of new electron shells.
  • Cations are smaller than their parent atoms; anions are larger.

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Full Notes

Key Concepts

The physical and chemical propertiesThe arrangement of electrons in shellsAtomic size decreases across a periodElements are classified into sElements like lithium

Frequently Asked Questions

What are the important topics in Periodic Table and Atomic Properties for Telangana Open School (TOSS) Class 12 Chemistry?
Periodic Table and Atomic Properties covers several key topics that are frequently asked in Telangana Open School (TOSS) 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 Periodic Table and Atomic Properties — Telangana Open School (TOSS) Class 12 Chemistry?
Understand the core concepts first, then work through the 43 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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