Periodic Table

Mendeleev's 1869 arrangement of all 118 elements by atomic number; the map of matter

Russia 🇷🇺 1869 Chemistry

Key Facts

1
Dmitri Mendeleev (1869) arranged 63 known elements by atomic mass; predicted 3 missing ones
2
Modern table ordered by atomic number (protons); 118 elements confirmed; 94 occur naturally
3
Periods (rows): electron shells; Groups (columns): similar chemical properties; Noble gases (Group 18) are inert

🔬 Did you know? Mendeleev left gaps in his table for undiscovered elements and predicted their properties — all three (gallium, scandium, germanium) were found within 15 years

Periodic Table

Key Facts

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