Topic Details (Notes format)

Periodic Classification of Elements

Subject: General Science

Book: NCERT Science Class 10

Elements are arranged in a systematic manner based on their properties.
- **Early Classification**:
- Dobereiner’s Triads.
- Newlands’ Law of Octaves.
- **Modern Periodic Table** (Mendeleev and Moseley):
- Elements arranged in increasing atomic number.
- Groups (columns) and Periods (rows).
- Predicts properties of elements.
- **Trends in the Periodic Table**:
- Atomic size, Electronegativity, Metallic & Non-metallic properties.

**Possible Exam Questions:**
1. Explain Mendeleev’s Periodic Law and its limitations.
2. What are Dobereiner’s Triads? Give an example.
3. How do atomic size and electronegativity change across a period?
4. What is the significance of the modern periodic table?
5. How does the reactivity of metals and non-metals change in a group?