Interactive Periodic Table
How to use the periodic table
- Click any element to see its atomic weight, group, period, block, family, electron configuration and electronegativity.
- Type a name, symbol or atomic number under Find an element to pick it out of the table.
- Color the table by family, by s, p, d and f block, or by electronegativity to see how the elements change across a period and down a group.
Frequently asked questions
Why are some atomic weights in brackets?
Elements with no stable isotope, such as technetium, promethium and everything from polonium on except thorium, protactinium and uranium, have no standard atomic weight. The number in brackets is the mass number of the longest-lived isotope.
Why is chromium 3d⁵ 4s¹ and not 3d⁴ 4s²?
A half-filled or filled d subshell is lower in energy, so chromium and copper move one electron from 4s into 3d. The table gives the measured ground-state configuration with these exceptions, and marks the predicted ones for the heaviest elements.
How do I get the molar mass of a compound?
Add up the atomic weights of every atom in the formula, or type the formula into the Molar Mass Calculator, which also shows the mass percent of each element.