What is the Periodic Table?
The periodic table is one of the most important tools in chemistry. It's a systematic arrangement of all known chemical elements in order of increasing atomic number—the number of protons in an element's nucleus. The table is designed so that elements with similar chemical properties are aligned in vertical columns, called groups.
How to Read the Table
Each tile on our interactive table provides key information about an element:
- Atomic Number: The integer at the top of the tile. It defines the element and is equal to the number of protons in its nucleus.
- Symbol: The one or two-letter abbreviation for the element (e.g., H for Hydrogen, Fe for Iron).
- Name: The full name of the element.
- Color Coding: The background color of each tile represents its chemical category, helping you quickly identify groups of similar elements.
Click on any element to open a detailed view with its atomic mass, discovery history, summary, and common uses.
Understanding Groups and Periods
The table's structure is not random; it's a map of the elements' atomic structures.
- Periods (Rows): The horizontal rows are called periods. Elements in the same period have the same number of electron shells. As you move from left to right across a period, elements become less metallic.
- Groups (Columns): The vertical columns are called groups. Elements in the same group have the same number of electrons in their outermost shell (valence electrons), which gives them similar chemical behaviors. For example, Group 18 contains the noble gases, which are all highly unreactive.
A Guide to Element Categories
The colors on the table help distinguish different families of elements, each with its own unique set of properties:
- Alkali Metals: Highly reactive, soft metals in Group 1.
- Alkaline Earth Metals: Reactive metals in Group 2, but less so than alkali metals.
- Transition Metals: The large central block (d-block) of hard, dense metals like iron, copper, and gold.
- Lanthanides & Actinides: The two rows at the bottom (f-block), often called inner transition metals. Many actinides are radioactive.
- Reactive Nonmetals: Includes elements essential for life, like Carbon, Nitrogen, and Oxygen.
- Noble Gases: The elements in Group 18, which are colorless, odorless, and extremely unreactive.