The Periodic Table
A tabular arrangement of the chemical elements ordered by atomic number.
5 min readUpdated July 16, 2026
Structure
Elements are arranged in rows called periods and columns called groups. Elements in the same group tend to have similar chemical properties.
History
Dmitri Mendeleev published the first widely recognized periodic table in 1869, famously predicting the properties of elements not yet discovered.
Reading the table
Each cell shows the element's symbol, atomic number (number of protons), and atomic mass. Metals are on the left, non-metals on the right, and metalloids form a diagonal band between them.