Periodic Table of Elements
Click any element for detailed information — atomic mass, electron configuration and more
About the Periodic Table
The periodic table organises all known chemical elements by atomic number (number of protons), electron configuration, and recurring chemical properties. Elements are arranged in rows (periods) and columns (groups), with elements in the same group sharing similar properties.
Reading the Table
Each cell shows the element's atomic number (top), chemical symbol (centre), name and atomic mass (bottom). Elements in the same column (group) have the same number of valence electrons and similar chemical behaviour. Elements in the same row (period) have the same number of electron shells.
Why the Gaps?
The two rows at the bottom (lanthanides and actinides) are removed from the main table to keep it compact. They belong between elements 56/88 and 72/104 respectively. The gaps in periods 1–3 represent groups where no elements with that configuration exist for lighter atoms.
From the Blog
How to Actually Read the Periodic Table
Built and verified by Andrius R. · Updated June 2026
The periodic table isn't a list — it's a map, and its weird castle-with-towers shape is the point. Position encodes behavior: read where an element sits and you can predict how it reacts before knowing anything else about it.
What a single cell tells you
Each tile carries the atomic number (protons — the element's identity; change it and you have a different element), the symbol (sometimes from Latin, hence Fe for iron/ferrum, Au for gold/aurum, Pb for lead/plumbum — the ancestor of "plumbing"), and the atomic mass (protons + neutrons, averaged across natural isotopes, which is why it's rarely a whole number: chlorine's 35.45 reflects a 3:1 mix of mass-35 and mass-37 atoms).
Rows and columns mean different things
- Periods (rows) count electron shells: each row adds one. Crossing a row left to right, elements shift from metal to nonmetal as the outer shell fills.
- Groups (columns) share the same number of outer-shell electrons — and since chemistry is almost entirely outer-electron behavior, columns are families. This is the table's superpower: sodium and potassium react alike (group 1); chlorine and iodine alike (group 17). Mendeleev trusted the pattern so much in 1869 that he left gaps and predicted the missing elements' properties — gallium and germanium arrived within two decades, matching his predictions, which is what turned a chart into a law.
The neighborhoods worth knowing
| Region | Members | Character |
|---|---|---|
| Alkali metals (group 1) | Li, Na, K… | One spare electron, desperate to lose it — react violently with water, never found pure in nature |
| Halogens (group 17) | F, Cl, Br, I | One electron short, aggressive takers — fluorine is the most reactive element known |
| Noble gases (group 18) | He, Ne, Ar… | Full shells, want nothing — chemistry's contented retirees, which is exactly why balloons and bulbs use them |
| Transition metals (middle block) | Fe, Cu, Au… | The workhorse metals: conductive, colorful compounds, multiple personalities (oxidation states) |
| The two detached rows | Lanthanides & actinides | Belong inside the table at periods 6–7; parked below purely so the chart fits on paper |
The most chemically dramatic pairings sit at the table's edges: group 1 + group 17 = the eager giver meets the eager taker — which is how violently reactive sodium and toxic chlorine combine into table salt.
Trends you can read off the geometry
Three gradients run across the map: atomic size grows down and shrinks rightward across a row (more pull from the nucleus); electronegativity (electron greed) climbs toward the top-right, peaking at fluorine; metallic character climbs toward the bottom-left. So the staircase line from boron to astatine isn't decoration — it's the metal/nonmetal coastline, with the semiconductors (silicon, germanium) sitting exactly on the beach, which is why your electronics are built from them.
Where the elements end (so far)
Everything past uranium (92) is human-made; the table currently stops at oganesson (118), completing period 7 in 2016. The heaviest elements exist for milliseconds, made atoms-at-a-time in accelerators — and the chase continues toward a predicted "island of stability" where certain proton/neutron counts might live longer. Period 8 awaits its first resident; the map above, in other words, is still being drawn.
// Mendeleev's Table
Dmitri Mendeleev published the first periodic table in 1869, leaving gaps for undiscovered elements. Three were found within his lifetime — gallium, scandium and germanium.
// Most Abundant
Oxygen is the most abundant element in Earth's crust (46%). In the universe, hydrogen dominates at ~75% by mass.
// Noble Gases
Noble gases (group 18) have full outer electron shells, making them almost entirely unreactive. Helium never forms compounds under normal conditions.
// Newest Elements
Elements 113–118 (Nihonium to Oganesson) were confirmed between 2015–2016. All are synthetic and highly radioactive with very short half-lives.