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What is the periodic table?

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Quick answer

The periodic table is a chart that organizes all the known chemical elements by their atomic number and shared properties. It lets scientists predict how elements behave and react. Elements are arranged by increasing number of protons (atomic number). Columns (groups) share similar chemical properties; rows are periods.

Key things to understand

  1. Elements are arranged by increasing number of protons (atomic number).
  2. Columns (groups) share similar chemical properties; rows are periods.
  3. Position predicts reactivity, bonding, and whether an element is a metal, nonmetal, or metalloid.
  4. It was devised by Dmitri Mendeleev, who even predicted undiscovered elements.

People also ask

How is the periodic table organized?
By atomic number, with elements of similar properties grouped in vertical columns.
What are groups and periods?
Groups are the columns (similar properties); periods are the rows (same number of electron shells).
Who created the periodic table?
Dmitri Mendeleev in 1869, arranging elements so patterns in their properties lined up.