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The Periodic Table — Flashcards

ICSE · Class 9 · Chemistry

48 flashcards for The Periodic Table (ICSE Class 9 Chemistry) to test yourself on key terms and facts. Sample: "Why is classification of elements needed?"

44 questions48 flashcards5 concepts

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An infographic explaining the historical need and benefits of classifying elements, such as ease of study, prediction of properties, and systematic organization.
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48 Flashcards·
Need for classificationEarly classificationAtomic mass as basisDobereiner's triadsDobereiner triad calculation
Card 1Need for classification

Why is classification of elements needed?

Answer

Classification helps in studying elements in an organized way, relating their properties, and understanding how one element is connected to another.

Card 2Early classification

What was the earliest basis used for classifying elements?

Answer

Early classification used factors such as density, malleability, ductility, and whether elements were metals or non-metals, but these were not satisfactory because they did not give a complete pattern…

Card 3Atomic mass as basis

What scientific basis was later found better for classifying elements?

Answer

Atomic mass was found to be a better basis because it does not vary under normal conditions and can be used to compare elements in a scientific way.

Card 4Dobereiner's triads

What is Dobereiner's law of triads?

Answer

"The atomic mass of the middle element of a triad was approximately equal to the arithmetic mean (average) of the atomic masses of the other two elements of that triad."…

Card 5Dobereiner triad calculation

Find the mean atomic mass for Ca and Ba in the triad Ca, Sr, Ba.

Answer

Formula: mean = (40 + 137) / 2 = 177 / 2 = 88.5. This is nearly equal to the atomic mass of Sr, which is 88.

Card 6Dobereiner triad calculation

Find the mean atomic mass for Cl and I in the triad Cl, Br, I.

Answer

Formula: mean = (35.5 + 127) / 2 = 162.5 / 2 = 81.25. This is nearly equal to the atomic mass of Br, which is 80.

Card 7Dobereiner's triads

Why did Dobereiner's law fail?

Answer

Dobereiner's law failed because it could not arrange all known elements into triads, and it did not work fully even within the same family, such as for F, Cl, and Br.

Card 8Dobereiner's triads

What is the failure shown by the halogen triad F, Cl, Br?

Answer

The mean of F and Br is 49.5, but Cl has atomic mass 35.5. So the middle element is not close to the average, showing the law does not hold here.

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Frequently Asked Questions

What are the important topics in The Periodic Table for ICSE Class 9 Chemistry?
Key topics in The Periodic Table include Need for Classification and Early Attempts, Dobereiner's Triads, Newland's Law of Octaves, Mendeleev's Periodic Table. Study these first, then practise questions on each for Class 9 exams.
How many flashcards are available for The Periodic Table?
There are 48 flashcards for The Periodic Table covering key definitions, facts and ideas. A few sample cards are shown on this page.
How should I revise The Periodic Table for Class 9 exams?
Learn the core ideas first, then work through the 44 practice questions on The Periodic Table. Revise definitions regularly and use flashcards for quick recall before the exam.

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