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Periodic Table

Mendeleev's 1869 organization of all matter — with gaps that predicted undiscovered elements.

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Dmitri Mendeleev published his Periodic Table of Elements in 1869, organizing the 63 then-known elements by atomic weight and chemical properties. Most remarkably, he left gaps for elements that hadn't yet been discovered — predicting their properties with such precision that when they were found (gallium, 1875; scandium, 1879; germanium, 1886), they matched his predictions almost exactly. The modern periodic table contains 118 confirmed elements (last additions: oganesson, 2016). It reveals that all matter in the universe is made of these building blocks in various combinations. Hydrogen (element 1) is the universe's most abundant element; oxygen, carbon, and nitrogen are the primary elements of life. Technetium (element 43) and promethium (element 61) have no stable isotopes — they exist only briefly.

# Top 10 Periodic Table facts

  1. 1Mendeleev's Periodic Table had gaps — he predicted three undiscovered elements, all found within 17 years
  2. 2Element 43 (technetium) doesn't exist naturally on Earth — it only occurs as a fission product in nuclear reactors
  3. 3The newest elements (numbers 113–118) were created artificially and exist for less than a second

Fascinating Facts

  • Mendeleev's Periodic Table had gaps — he predicted three undiscovered elements, all found within 17 years
  • Element 43 (technetium) doesn't exist naturally on Earth — it only occurs as a fission product in nuclear reactors
  • The newest elements (numbers 113–118) were created artificially and exist for less than a second
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