The periodic table was invented by Russian chemist Dmitri Mendeleev in 1869.
His table organized the then-known elements by atomic weight and properties. Its key innovation was leaving spaces for elements that had not yet been discovered, which were later found to match his predictions.
There are currently 118 known elements in the periodic table, with hydrogen being the first and oganesson being the last.
While 94 of these occur naturally on Earth, the remaining 24 have been synthesized in laboratories.
The elements are organized by their atomic number (number of protons).
It depicts the periodic law: elements arranged by atomic number show recurring properties. The table is divided into four blocks, and elements in the same group share chemical characteristics.
Vertical, horizontal, and diagonal trends characterize the table.