Interactive Periodic Table

The Periodic Table of Elements is one of the most powerful tools in science. Organized by increasing atomic number, it arranges all 118 known chemical elements in rows (periods) and columns (groups) in a way that reveals recurring patterns in their physical and chemical properties — a phenomenon known as periodicity.

The table was first systematically arranged by Russian chemist Dmitri Mendeleev in 1869. His genius was not just in organizing the known elements, but in confidently leaving gaps for elements that had not yet been discovered — correctly predicting their properties based on the patterns he observed. His predictions for gallium, germanium, and scandium were later confirmed experimentally, validating the periodic law.

How to Read the Periodic Table

• Atomic Number — the number of protons in an atom's nucleus. This uniquely identifies each element and increases by 1 across the table.
• Atomic Mass — the weighted average mass of an element's naturally occurring isotopes, measured in atomic mass units (u).
• Periods (rows) — elements in the same row have the same number of electron shells. As you move left to right, atomic number increases and properties change systematically.
• Groups (columns) — elements in the same column share similar electron configurations in their outermost shell, producing similar chemical reactivity.
• Electron Configuration — describes how electrons are distributed across atomic orbitals, determining an element's bonding behavior and reactivity.

Element Categories

• Alkali Metals (Group 1) — highly reactive, soft metals that react vigorously with water (Li, Na, K, Rb, Cs, Fr)
• Alkaline Earth Metals (Group 2) — reactive metals that form basic oxides (Be, Mg, Ca, Sr, Ba, Ra)
• Transition Metals (Groups 3–12) — hard, lustrous metals with high melting points; include iron, gold, copper, and platinum
• Lanthanides & Actinides — rare earth elements and radioactive heavy elements displayed separately at the bottom
• Metalloids — semiconductors with mixed properties of metals and nonmetals (Si, Ge, As, Sb, Te, Po)
• Halogens (Group 17) — highly reactive nonmetals that form salts with metals (F, Cl, Br, I, At)
• Noble Gases (Group 18) — extremely stable, colorless gases with full outer electron shells (He, Ne, Ar, Kr, Xe, Rn)

Key Trends Across the Table

• Electronegativity increases from left to right and bottom to top; fluorine (F) is the most electronegative element
• Atomic radius generally decreases left to right (more protons pulling electrons inward) and increases top to bottom (more electron shells)
• Ionization energy — the energy required to remove an electron — increases across a period and decreases down a group
• Metallic character decreases left to right; most elements are metals, with nonmetals concentrated in the upper-right corner