Latest Updated CBSE Class 10 Science CH-05 Periodic Classification of Elements

November 26, 2024 ,

CBSE Class 10 Science Notes Chapter 5 Periodic Classification of Elements


CBSE Class 10 Science Notes

Chapter 5: Periodic Classification of Elements

  1. History of Classification

    • Dobereiner’s Triads: Elements grouped into triads based on similar properties. E.g., Li, Na, K.
    • Newlands’ Law of Octaves: Properties repeat every eighth element but fail beyond calcium.
    • Mendeleev’s Periodic Table: Based on atomic mass; left gaps for undiscovered elements.

  2. Modern Periodic Table

    • Based on increasing atomic number.
    • Groups (1-18) & Periods (1-7).
    • Metals, non-metals, and metalloids are classified separately.

  3. Trends in the Periodic Table

    • Atomic Size: Decreases across a period, increases down a group.
    • Ionization Energy: Increases across a period, decreases down a group.
    • Electronegativity: Increases across a period, decreases down a group.
    • Metallic vs. Non-metallic Character: Metallic character decreases across a period.

  4. Significance

    • Predicts properties of elements and their compounds.
    • Explains chemical reactivity trends.

Most Important Science Class 10 Questions Answers For the 2025 Board Examination

Top Most Asked Questions and Answers

Chapter 5: Periodic Classification of Elements

  1. Why did Mendeleev leave gaps in his periodic table?
    Mendeleev left gaps to accommodate undiscovered elements, predicting their properties. For example, he predicted the existence and properties of germanium (eka-silicon).

  2. State Modern Periodic Law.
    The properties of elements are a periodic function of their atomic numbers.

  3. Trends in Atomic Size:

    • Decreases across a period due to increasing nuclear charge.
    • Increases down a group due to added shells.

  4. Why do noble gases have zero valency?
    Noble gases have a stable electronic configuration with a complete outer shell (octet).

Most Important MCQs Science Class 10 For the 2025 Board Examination

MCQs on Chapter 5: Periodic Classification of Elements

  1. Who proposed the Modern Periodic Table?
    A. Dmitri Mendeleev
    B. John Newlands
    C. Henry Moseley
    D. Antoine Lavoisier
    Answer: C

  2. In the Modern Periodic Table, elements are arranged in order of:
    A. Increasing atomic mass
    B. Increasing atomic number
    C. Decreasing atomic number
    D. Increasing valency
    Answer: B

  3. Which of the following is a halogen?
    A. Sodium
    B. Bromine
    C. Magnesium
    D. Argon
    Answer: B

  4. Atomic size decreases across a period because:
    A. Number of shells increases
    B. Nuclear charge increases
    C. Valence electrons increase
    D. Atomic mass increases
    Answer: B

  5. The element in Group 2, Period 3 of the Modern Periodic Table is:
    A. Magnesium
    B. Calcium
    C. Sodium
    D. Potassium
    Answer: A

  6. Which element has the highest electronegativity in the periodic table?
    A. Fluorine
    B. Oxygen
    C. Nitrogen
    D. Chlorine
    Answer: A

  7. An element with atomic number 15 belongs to which group in the Modern Periodic Table?
    A. Group 13
    B. Group 14
    C. Group 15
    D. Group 16
    Answer: C

  8. Which property increases down a group in the Modern Periodic Table?
    A. Ionization energy
    B. Electronegativity
    C. Metallic character
    D. Non-metallic character
    Answer: C


Board Exam Class 10 Science Revision Notes




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