PrepOK

Drag a point around the Cartesian grid to read its (x, y) coordinates and quadrant, snap to whole numbers, and reveal its reflections across the x-axis, y-axis, and origin.

Hover or arrow-key across a 12×12 multiplication chart to light up any times-table fact, with an area model that shows why a × b is a rectangle of that many squares.

Drag a point around the unit circle to see the angle in degrees and radians, plus sine, cosine, and tangent — with exact values at common angles like 30°, 45°, and 60°.

See why atomic mass is a decimal: it is the abundance-weighted average of an element's isotopes. Slide the isotope mix for chlorine, boron, or copper and watch the average.

Compare two atoms to see δ+/δ−, the dipole arrow, ΔEN, and bond type — then check whether a whole molecule is polar or cancels by symmetry.

Pick any element from hydrogen to krypton and watch its ground-state electron configuration and Bohr shell diagram build up in Aufbau order — including the chromium and copper exceptions.

Build the Bohr model of any element (Z 1-118). Pick an atomic number to see the nucleus and electron shells fill, with electrons-per-shell and outer-shell count.

Explore all 118 elements in an interactive periodic table: recolor by category, state, or block, and open any element for its electron configuration, Bohr model, and uses.

Slide across the 0–14 pH scale to see each value's acidity classification, its hydrogen-ion concentration [H⁺] = 10⁻ᵖᴴ, and a familiar everyday substance at that pH.

Pick two elements and compare their electronegativity. The ΔEN difference predicts an ionic, covalent (polar or nonpolar), or metallic bond.

Draw the Lewis dot structure of common molecules. See bonds as lines, lone pairs as dots, count valence electrons, and meet the octet-rule exceptions.

Pick a molecule and watch VSEPR predict its 3D shape. See how lone pairs and bonding regions set the geometry, bond angle, and hybridization.

A free build-a-molecule game: tap atoms into the tray, bond them, and watch real molecules snap together. Take on challenges or free-build to discover all 14.

Explore the noble gases of group 18 — helium, neon, argon, krypton, xenon, radon, and oganesson — and see why a full outer shell makes them so unreactive.

A free, fast periodic table game — we name an element, you race to click it on the table. Beat your best time, learn where every element lives, no signup.

Color the periodic table by electronegativity, ionization energy, or electron affinity. See how each trend moves across periods and down groups.

Pick a main-group element and see its Lewis electron-dot symbol. Learn the group rule that gives valence electrons for groups 1, 2, and 13 to 18.

Set any two of voltage, current, and resistance and watch the third solve itself with V = I × R. A live circuit lights a bulb whose brightness tracks the power.

Animate a travelling wave, adjust its amplitude, wavelength, and frequency, switch between transverse and longitudinal motion, and watch wave speed (v = f × λ) and period (T = 1/f) update live.

Slide along the electromagnetic spectrum from radio waves to gamma rays and watch wavelength, frequency, and photon energy update together — with a rainbow swatch in the visible band.

Click or tab through a labeled animal cell to explore the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, ribosomes, lysosome, vacuole, and more — each with its job explained.

Click through an interactive water-cycle scene — evaporation, condensation, precipitation, and collection (plus transpiration and runoff) — with a kid-friendly explanation for each stage.