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Lekce 6 · třída 7–9
The periodic table: the map of elements
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Everything is built from ~118 elements — like words from letters. Mendeleev arranged them in a table: rows are periods, columns groups with similar character. Noble gases on the right are lazy and react with no one; metals on the left give electrons and flare up. The atomic number equals the proton count.
- ●H (1) — hydrogen, the lightest
- ●Fe (26) — iron, Au (79) — gold
- ●Groups are families: Li, Na, K — all reactive metals
🧪 Mendeleev saw the table in a dream — and left empty cells for undiscovered elements. They were found later exactly there.