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Periodic Table and Periodicity in Properties

NIOS · Class 12 · Chemistry

Complete topic list for Periodic Table and Periodicity in Properties in NIOS Class 12 Chemistry. Key concepts, sub-topics, and what to focus on for board exams.

45 questions30 flashcards5 concepts

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A diagram illustrating Dobereiner's Law of Triads with specific examples, showing three elements with similar properties where the atomic mass of the middle element is approximately the average of the
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4 Topics · NIOS Class 12 Chemistry

Topics in Periodic Table and Periodicity in Properties

1

Early Attempts at Classification of Elements

  • Dobereiner's Triads (1817): Elements grouped in sets of three where the atomic weight of the middle element is approximately the arithmetic mean of the other two. Example: Li (6.94), Na (22.99), K (39
  • Limitation of Dobereiner's Triads: Could only classify a few elements; insufficient data on atomic weights at that time.
  • Newlands' Law of Octaves (1863): Elements arranged in increasing order of atomic weights; every eighth element had similar properties to the first — like musical octaves (sa, re, ga...). Example: Li a
2

Mendeleev's Periodic Table

  • Mendeleev (1869) arranged elements in increasing order of atomic weights and grouped elements with similar chemical properties in the same vertical column (group).
  • Mendeleev's Periodic Law: 'The properties of elements are periodic functions of their atomic weights.'
  • Mendeleev's table had 8 groups (I to VIII) and several periods.
3

Modern Periodic Law and Long Form of the Periodic Table

  • Moseley (1913) discovered that atomic number (number of protons) is the fundamental property of an element, not atomic weight. He changed the basis of the periodic table.
  • Modern Periodic Law: 'The properties of elements are periodic functions of their atomic numbers.'
  • This solved all the defects of Mendeleev's table — isotopes got the same place (same atomic number), and anomalous pairs like Co-Ni were correctly arranged.
4

IUPAC Nomenclature for Elements with Atomic Number > 100

  • For elements with atomic number greater than 100 (and specifically used for > 103), IUPAC (1994/1997) developed a systematic naming system to avoid naming disputes.
  • Numerical roots used: 0=nil, 1=un, 2=bi, 3=tri, 4=quad, 5=pent, 6=hex, 7=sept, 8=oct, 9=enn.
  • Rule: Write the roots for each digit of the atomic number in order, then add 'ium' at the end.

Key Concepts

Dobereiner discovered that certain elements couldJohn Newlands arranged elements in orderDmitri Mendeleev arranged elements by increasingIn 1913The modern periodic table perfectly matches

Frequently Asked Questions

What are the important topics in Periodic Table and Periodicity in Properties for NIOS Class 12 Chemistry?
Key topics in Periodic Table and Periodicity in Properties include Periodic Table and Periodicity in Properties - Complete Chapter Overview, Periodic Table and Periodicity Concepts Overview, Shows the structure of Dobereiner's triads and how the mathematical relationship works with the lithium-sodium-potassium example. These are the concepts NIOS Class 12 examiners draw on most — study them first, then practise related questions.
How to score full marks in Periodic Table and Periodicity in Properties — NIOS 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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