Interactive Periodic Table

How to Read the Periodic Table

The periodic table arranges every known element by atomic number — the number of protons in its nucleus — in a grid where position tells you a lot about how the element behaves chemically.

• Periods (rows) — the seven horizontal rows correspond to the number of electron shells an atom has. Elements in period 1 have electrons in just one shell; elements in period 7 have electrons spread across seven.
• Groups (columns) — the 18 vertical columns group elements with similar numbers of outer (valence) electrons, which is why elements in the same group tend to react in similar ways. Group 1 (alkali metals) and Group 17 (halogens) are both famously reactive, just in opposite directions.
• Blocks — the table is also divided into s-, p-, d-, and f-blocks based on which type of electron orbital is being filled. The two rows pulled out below the main table (the lanthanides and actinides) are the f-block, shown separately purely to keep the table from becoming impractically wide.

Every cell in the grid above shows the element's atomic number and symbol. Click one to see its full name, standard atomic mass, category, and physical state at room temperature.

Element Categories Explained

This tool color-codes elements into 11 broad categories (matching the legend above the table):

• Alkali metals — soft, extremely reactive metals in Group 1 (excluding hydrogen) that react violently with water.
• Alkaline earth metals — Group 2 metals, reactive but less so than alkali metals.
• Transition metals — the large central block including iron, copper, gold, and silver; typically hard, conductive, and able to form multiple oxidation states.
• Post-transition metals — metals to the right of the transition block (like aluminum, tin, and lead) that are softer and lower-melting than transition metals.
• Metalloids — elements like silicon and germanium with properties between metals and nonmetals, many of which are essential semiconductors.
• Nonmetals — elements such as carbon, nitrogen, and oxygen that are typically poor conductors and essential to organic chemistry and life.
• Halogens — highly reactive nonmetals in Group 17 (fluorine, chlorine, bromine, iodine) that readily form salts with metals.
• Noble gases — Group 18 elements that are essentially chemically inert under normal conditions.
• Lanthanides — the first f-block row (elements 57–71), often called "rare earth" elements and used heavily in magnets, batteries, and electronics.
• Actinides — the second f-block row (elements 89–103), all radioactive; only thorium and uranium occur in significant natural quantities.
• Unknown properties — a handful of the newest, heaviest synthetic elements that have only ever existed as a few atoms for fractions of a second, too briefly to measure most physical properties directly.

Frequently Asked Questions

What's the difference between atomic number and atomic mass?

Atomic number is a whole number — the count of protons in the nucleus, which defines the element. Atomic mass (or atomic weight) is a decimal value representing the weighted average mass of an element's naturally occurring isotopes, measured in atomic mass units (u). Hydrogen has atomic number 1 but an atomic mass of about 1.008 because a small fraction of natural hydrogen atoms are heavier isotopes like deuterium.

Why are the lanthanides and actinides shown in separate rows below the table?

Purely for practical layout. If all 118 elements were placed in their true position, the periodic table would need 32 columns instead of 18, making it far too wide to print or display comfortably. Pulling the f-block (lanthanides and actinides) into two rows below keeps the table a manageable, standard shape without changing the underlying chemistry.

What does "metalloid" mean?

Metalloids sit along the zig-zag staircase line between metals and nonmetals on the table (elements like boron, silicon, and arsenic) and share properties of both — for example, many conduct electricity better than nonmetals but worse than true metals, which is exactly why silicon and germanium are the backbone of semiconductor electronics.

Are the elements past 104 even real? Why are their properties "unknown"?

Yes — elements 104 and beyond have all been confirmed to exist, but only by creating a handful of atoms at a time in particle accelerators, and those atoms typically decay within seconds or even milliseconds. That's far too little material and too little time to directly measure properties like melting point or density, so category assignments for the heaviest elements are based on predicted chemical behavior rather than direct observation.

Why is hydrogen placed above Group 1 with the alkali metals?

Hydrogen has just one electron, the same outer-shell electron count as the alkali metals, which is why it's conventionally placed above Group 1. But chemically it behaves quite differently — it's a gas, not a reactive metal — so some periodic tables place it separately, or even show it above the halogens (Group 17) instead, since it can also gain an electron like a halogen does. This tool follows the most common convention and places it in Group 1.

Is my data uploaded anywhere when I use this tool?

No. All element data is built into the page itself — searching, filtering, and clicking elements all happen locally in your browser with nothing sent to a server.