Repeating Patterns The Modern Periodic Table

In nature, as well as in things that humankind invents, you may notice some repeating patterns. The seasons repeat their pattern of fall, winter, spring, and summer. The tides repeat their pattern of rising and falling. Tuesday follows Monday, December follows November, and so on. A pattern of repeating order is called periodicity. 

In the mid-1800s, Dmitri Mendeleev, a Russian chemist, noticed a repeating pattern of chemical properties in the elements that were known at the time. Mendeleev arranged the elements in 

Thorium Protactinium Uranium Neptunium Plutonium Americium 

Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton 

Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon 

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