Interactive periodic table

The table arranges elements by atomic number (the number of protons), from hydrogen (1) to oganesson (118).

• Periods are the 7 rows. Elements in the same period have the same number of electron shells.
• Groups are the 18 columns. Elements in a group have similar outer electrons and behave similarly: group 1 alkali metals react strongly with water, group 18 noble gases barely react at all.
• The two rows below the table are the lanthanides and actinides, which belong in periods 6 and 7 but are placed separately to keep the table a practical width.

Colors show the category of each element: alkali metal, alkaline earth metal, transition metal, post-transition metal, metalloid, nonmetal, halogen, noble gas, lanthanide and actinide. Click a category button to highlight just those elements.

Select an element to see:

• atomic number and symbol, e.g. 26 Fe for iron,
• atomic mass, the IUPAC standard atomic weight (abridged), e.g. 55.845,
• category, period and group,
• state at room temperature: gas, liquid (only bromine and mercury) or solid,
• molar mass in g/mol, which numerically equals the atomic mass.

For radioactive elements with no stable isotope, such as technetium or plutonium, the value in brackets is the mass number of the longest-lived known isotope, e.g. [244] for plutonium. For elements from 100 (fermium) onward, the state is listed as unknown, because only a few atoms have ever been made.

Type a chemical formula and the tool adds up the atomic masses:

Example: sulfuric acid, H2SO4

Element	Atoms	g/mol	Mass %
H (hydrogen)	2	2.016	2.06%
S (sulfur)	1	32.06	32.69%
O (oxygen)	4	63.996	65.25%
Total		98.072 g/mol	100%

The calculator understands:

• parentheses and brackets: Ca(OH)2, Al2(SO4)3, K4[Fe(CN)6],
• hydrates with a dot or asterisk: CuSO4·5H2O or CuSO4*5H2O,
• charges at the end, which are ignored: SO4^2-, NH4+,
• subscript digits pasted from documents: H₂O.

Case matters: CO is carbon monoxide, Co is cobalt. Element symbols always start with a capital letter.

Molar mass connects grams and moles: moles = mass ÷ molar mass.

Example: how many moles are in 10 g of table salt (NaCl)? The molar mass is 22.99 + 35.45 = 58.44 g/mol, so 10 ÷ 58.44 = 0.171 mol.

The other way: how many grams are in 0.5 mol of water (H2O, 18.015 g/mol)? 0.5 × 18.015 = 9.01 g.

The mass percent column answers composition questions directly, for example the share of oxygen in water (88.8%) or of nitrogen in a fertilizer such as ammonium nitrate, NH4NO3 (35.0%).

Atomic masses are the abridged standard atomic weights published by IUPAC's Commission on Isotopic Abundances and Atomic Weights (CIAAW). For elements like hydrogen, carbon and oxygen, the natural isotope mix varies slightly, so IUPAC publishes a conventional single value, which is what is shown here.

Textbooks and exams often use rounded values, such as Cl = 35.5 or O = 16, so your result may differ from the answer key in the tenths or hundredths. Use the values your course specifies when that matters.