Elements and Compounds
PART-A Unit-I: General Science
Previous Year Questions (PYQ) for this topic
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Chemistry - Important Notes - PYQ Points
1. Periodic Table
- Law of Octaves: The Law of Octaves for arranging elements was proposed by Newlands.
- Modern Periodic Law: Moseley stated that the properties of elements depend on their atomic number.
- Blocks:
• d-block: Known as "Transition Elements".
• p-block: The only block that contains metals, non-metals, and metalloids. - Statistics: The modern periodic table contains a total of 118 elements (94 occur naturally).
2. Properties of Elements and Compounds
| Element / Compound | Key Property / Use |
|---|---|
| Bromine (Br) | The only non-metal that exists in liquid state at room temperature. |
| Silicon Carbide | A compound that is extremely hard like diamond. |
| Solid CO₂ | Sprinkled over clouds to induce artificial rain (Dry ice). |
| Diamond | Has a high refractive index; used to cut glass. |
| Iodine | Insoluble in water. Mixed with alcohol to prepare 'Tincture Iodine'. |
3. Metallurgy
- Stages: Concentration of ore → Extraction of crude metal → Purification (refining) of metal.
- Iron (Hematite): Hematite is an iron oxide ore. It is
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