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Evolution of Classification of Elements

• Lavoisier (1789)
– Classified elements as metals and non-metals
– First step toward systematic classification

• Dobereiner (1817)
– Grouped elements into triads
– Elements in a triad had similar properties

• Newlands (1864)
– Arranged elements by atomic mass
– Every 8th element showed similar properties
– Called the Law of Octaves

• Mendeleev (1869)
– Arranged elements by atomic mass
– Placed similar elements in the same group
– Left gaps and predicted new elements

• Modern Periodic Table
– Based on atomic number
– Explains isotopes correctly
– Most accurate classification

Each step improved our understanding of elements.

✨ Divisibility Rules Made Super Easy! ✨
Tired of long division? Try these shortcuts instead ⬇️

🔢 Divisibility by 2 → Last digit even (0, 2, 4, 6, 8)
🔢 Divisibility by 3 → Sum of digits divisible by 3
🔢 Divisibility by 4 → Last 2 digits divisible by 4
🔢 Divisibility by 5 → Ends with 0 or 5
🔢 Divisibility by 6 → Divisible by both 2 and 3
🔢 Divisibility by 8 → Last 3 digits divisible by 8
🔢 Divisibility by 9 → Sum of digits divisible by 9
🔢 Divisibility by 10 → Ends with 0

⚡ Maths becomes easier when you know these magic rules! ⚡

📘 Save this for quick revision before exams