How to read the periodic table
Elements are arranged by increasing atomic number. Horizontal rows are periods, while vertical columns are groups. Elements in the same group often show related chemical behavior because they have similar outer-electron arrangements.
Atomic number
The whole number at the top of each tile is the number of protons in the nucleus. It uniquely identifies the element.
Chemical symbol
The large one- or two-letter abbreviation is used in formulas and equations. The first letter is uppercase; a second letter is lowercase.
Atomic mass
The lower value is a practical atomic-mass reference. Square brackets show a representative mass number for elements without a standard atomic weight.
Groups, periods, and element families
The table contains 18 groups and seven main periods. Alkali metals appear in group 1, halogens in group 17, and noble gases in group 18. The transition metals occupy the central block. Lanthanides and actinides belong to periods 6 and 7 but are displayed below the main table to keep it compact.
Use the colors to recognize broad families, then test whether you can identify the same elements without the layout in the free periodic table quiz. For a structured revision method, read the periodic table study guide.
Practice names, symbols, atomic numbers, and scientific clues.