Periodic Table
An interactive periodic table — tap any element for its number, symbol, and atomic mass.
The periodic table arranges all 118 elements by increasing atomic number, with columns (groups) sharing chemical behavior and rows (periods) sharing an outer electron shell. Each cell shows the atomic number, symbol, and average atomic mass — carbon, for example, is number 6, symbol C, mass 12.011 g/mol.
Reading the table
Elements are arranged by increasing atomic number, with columns (groups) sharing chemical behavior and rows (periods) sharing an outer electron shell. Colors mark categories — alkali metals, noble gases, halogens, and more. Tap any element to see its full details.
Worked example
Read everything in carbon’s cell — the basis of organic chemistry.
- 1 Find the atomic number. The top number is 6 — carbon has 6 protons (and 6 electrons when neutral).
- 2 Read the symbol and name. The large symbol is C, for carbon; group 14, period 2 — a nonmetal.
- 3 Read the atomic mass. The bottom value is 12.011 — the standard atomic weight in g/mol, used directly in molar-mass sums.
Element categories
Each color on the table marks one of these families.
| Category | Example | Trait |
|---|---|---|
| Alkali metals | Na, K | Group 1, very reactive |
| Alkaline earth | Mg, Ca | Group 2 metals |
| Transition metals | Fe, Cu | Central d-block |
| Halogens | F, Cl | Group 17, reactive non-metals |
| Noble gases | He, Ne | Group 18, inert |
| Lanthanides / actinides | La, U | f-block rows below |
Trends across the table
Periods and groups. Moving across a period (left to right), atoms gain protons and electrons in the same shell; moving down a group adds shells. This drives periodic trends in size, electronegativity, and reactivity.
The f-block is pulled out. The two rows below the main body are the lanthanides (57–71) and actinides (89–103), separated so the table stays a readable width.
Atomic mass vs mass number. The decimal mass on the table is the average atomic weight across natural isotopes, not the whole-number mass of a single isotope. For synthetic elements with no stable isotope, the value is the mass number of the most stable one. These standard atomic weights feed straight into the Molar Mass calculator when you sum a formula.