Development of the Periodic Table
Emade coins and jewelry from gold and silver. They also made tools and weapons from copper, tin, and iron. In the nineteenth centuryarly civilizations were familiar with a few of the substances now called elements. They , chemists began to search for new elements. By 1830, they had isolated and named 55 different elements. The list continues to grow today.
Dmitri Mendeleev published the first version of the periodic table in 1869. Mendeleev left three gaps on the periodic table for missing elements.
Moseley arranged Mendeleev’s table according to atomic number, not by atomic mass.
Today’s Periodic Table
• The periodic table is divided into sections.
• A period is a row of elements whose properties change gradually and predictably.
• Groups 1 and 2 along with Groups 13–18 are called representative elements.
• Groups 3–12 are called transition elements.