About the Interactive Periodic Table
This interactive periodic table shows all 118 elements in the standard 18-column layout, colour-coded by element family. Click or search any element — by symbol, name or atomic number — to see its atomic number, standard atomic weight, ground-state electron configuration, Pauling electronegativity, first ionization energy, group, period, block, physical state, melting and boiling points, density, most common isotope and year of discovery.
It is built for students learning periodic trends, teachers projecting a clean reference in class, and anyone who needs a quick, trustworthy number for a calculation. Atomic weights are the IUPAC CIAAW 2024 abridged standard atomic weights; for radioactive elements with no standard weight the mass number of a long-lived isotope is shown in brackets, as on printed tables.
Electronegativity, physical state, melting point, boiling point and density come from the PubChem periodic table (NIH), and first ionization energies from the NIST Atomic Spectra Database. The layout follows the IUPAC convention with lutetium and lawrencium in group 3 and the f-block series (La–Yb and Ac–No) shown below the main table. Values for the heaviest elements (above about Z = 104) are predictions, not measurements.
How to use the interactive periodic table
- 1Click any element tile, or type a symbol, name or atomic number in the search box.
- 2Read the atomic weight, electron configuration and other properties in the detail panel.
- 3Use the colour legend to spot element families such as halogens or noble gases.
- 4Compare neighbours to see trends in electronegativity and ionization energy.
Formula and method
The table orders elements by atomic number Z, the number of protons. Rows (periods) correspond to the highest occupied electron shell and columns (groups) collect elements with the same number of valence electrons, which is why elements in a group behave alike. Blocks (s, p, d, f) name the subshell being filled, following the Madelung (n + l) order with known exceptions such as Cr, Cu, Mo, Ag, Pt and Au.
The standard atomic weight is the abundance-weighted average mass of an element’s natural isotopes relative to 1/12 of carbon-12, so it is not a whole number. A specific isotope has mass number A = protons + neutrons. Electronegativity (Pauling scale) and first ionization energy rise across a period and fall down a group, the two most tested periodic trends.
- Z
- Atomic number (number of protons)
- A
- Mass number of an isotope (protons + neutrons)
Worked examples
Iron (Fe)
Iron is element 26, a transition metal in group 8, period 4. Its IUPAC standard atomic weight is 55.845 and its ground-state configuration is [Ar] 3d⁶ 4s². Its most common isotope is iron-56 (26 protons, 30 neutrons).
Gold, searched by name
Gold (Au, Z = 79) is an exception to the filling order: one 6s electron moves into 5d to give a full 5d¹⁰ subshell, [Xe] 4f¹⁴ 5d¹⁰ 6s¹. Its Pauling electronegativity of 2.54 is the highest of any metal.
Element 17 by atomic number
Atomic number 17 is chlorine, a halogen in group 17 of the p-block. IUPAC gives its abridged atomic weight as 35.45 because natural chlorine is about three-quarters Cl-35 and one-quarter Cl-37. Its first ionization energy is 12.968 eV.
Frequently asked questions
How many elements are on the periodic table?+
There are 118 confirmed elements, from hydrogen (Z = 1) to oganesson (Z = 118). The seventh period was completed when IUPAC named nihonium, moscovium, tennessine and oganesson in 2016.
Why is atomic mass not a whole number?+
The standard atomic weight is an average over an element’s naturally occurring isotopes, weighted by their abundance. Chlorine is about 76% Cl-35 and 24% Cl-37, which averages to 35.45. Individual isotopes have masses close to whole numbers.
What do the brackets around some atomic masses mean?+
Technetium, promethium and every element from polonium (Z = 84) upward except thorium, protactinium and uranium have no standard atomic weight, because they have no stable isotopes and no characteristic natural isotopic composition. The bracketed number is the mass number of a long-lived isotope, for example [145] for promethium or [244] for plutonium.
What are the trends in electronegativity and ionization energy?+
Both generally increase from left to right across a period, as nuclear charge grows, and decrease down a group, as outer electrons sit farther from the nucleus. Fluorine has the highest electronegativity (3.98) and helium the highest first ionization energy (24.59 eV).
Why are the lanthanides and actinides shown below the table?+
The f-block would make the table 32 columns wide, so its two series are printed separately to keep the layout readable. They belong in periods 6 and 7 between group 2 and group 3.
Where do these values come from?+
Atomic weights are IUPAC CIAAW 2024 abridged values; electronegativity, physical state, melting and boiling points and density are from the NIH PubChem periodic table; ionization energies are from NIST. Small differences from older textbooks reflect updated measurements.