Chemistry • Data Investigation
Periodicity Investigator
Use measured element data to discover how atomic size, first ionization energy, and electronegativity change across periods and down groups.
Interactive periodic table
Click any element for basic information. Elements with measured trend data are marked with a dot.
Element evidence
Select an element or a comparison set.
Carbon
Atomic number 6 • Period 2 • Group 14
Prediction challenge
Which has the larger covalent radius: Li or F?
Graph the pattern
Measured values expose both the overall trend and real exceptions.
Period 2 — Covalent radius
Measured values for the selected elements.
Build the explanation
Periodicity comes from repeating electron structures—not from a perfect diagonal arrow.
Effective nuclear attraction generally increases while electrons are added to the same principal energy level. Radius tends to decrease; ionization energy and electronegativity tend to increase.
Additional occupied energy levels place valence electrons farther from the nucleus and increase shielding. Radius tends to increase; ionization energy and electronegativity tend to decrease.
Subshell structure and electron pairing create local exceptions. Use the graph as evidence rather than memorizing a perfect arrow.
The table contains all 118 elements for context. Trend graphs use a curated set of measured classroom values for representative main-group elements; unavailable values are shown as “—”.