物质的游乐场。

晶体结构浏览器——旋转固态物质的基准固体，将晶胞重复扩展为超胞，并从 PubChem 拉取实时 3D 分子。

一份涵盖所有已知元素的空间索引——悬停查看速读，点击查看完整档案，按属性重新着色，并可旋转任意原子的玻尔模型。

握住一个分子细细端详——一个 3D 球棍模型库，你可以旋转、重新着色，并在空间填充、棍状和线框模型之间切换。

Why water is weird: a bent polar molecule and its restless hydrogen-bond network explain the 4 °C density maximum, ice that floats, high heat capacity and surface tension.

Water self-ionizes: Kw = [H⁺][OH⁻] climbs with temperature, so neutral pH drops below 7 in hot water.

Count bonding and lone pairs, watch electron-domain repulsion fold a molecule into its 3D shape — linear to octahedral.

Molecules evaporate and condense to a dynamic equilibrium; the vapor pressure climbs with temperature (Clausius–Clapeyron) and the liquid boils when it meets the external pressure.

Stretch a conjugated chain and watch λmax slide toward red — electronic π→π* transitions turn molecules into colour, the longer the conjugation the deeper the hue.

Cohesion versus adhesion in a 2D particle liquid — droplets minimise their surface, a wettable tube pulls water up while a non-wetting one pushes it down.

A thermostatted particle box that melts then boils as you add heat — watch the lattice break, the liquid flow, the gas fly apart, with phase-change plateaus.

Read spontaneity straight off the reduction-potential ladder: pick an oxidant and a reductant and see if E°cell is positive.

Molarity, dilution (M₁V₁ = M₂V₂), and acid–base neutralization volumes — mix and dilute solutions in a live beaker and read the moles of solute.

Dissolve a sparingly soluble salt, compute its molar solubility, and predict precipitation from Q vs Ksp — including the common-ion effect.

Plot grams of salt per 100 g water against temperature, saturate the solution, then cool it and watch the excess recrystallize.

Band theory of solids: the valence and conduction bands, the gap that sorts conductors from insulators, doping levels, and conductivity that climbs with temperature.

Why dissolved salts turn water acidic, basic, or neutral — solved from the Ka/Kb of each ion of the salt.

Cycle through the equivalent resonance forms of ozone, carbonate, nitrate or benzene and see them blur into one delocalized hybrid.

Balance redox reactions by the half-reaction method — split, balance atoms, equalise electrons, recombine — step by step in acid or base.

Watch the compressibility factor Z = PV/nRT peel away from 1 as van der Waals attraction and finite molecular volume take over at high pressure and low temperature.

Set the temperature, barrier and enthalpy, then watch rate and equilibrium emerge from molecular collisions.

Integrate the concentration–time curve for zero-, first- and second-order reactions and watch how the order controls the rate.

Build a multi-step energy profile with intermediates and transition states; the tallest barrier from a valley is the rate-determining step.

Vapor pressure of a mixture vs composition — a nonvolatile solute lowers it, two volatiles trace the bubble/dew lines that fractional distillation rides.

Watch a population of unstable nuclei thin out as N = N₀·e^(−λt), with α, β and γ emission rewriting Z and A.

The four addresses of an electron — n, ℓ, mₗ, mₛ — enumerated as a tree, with every subshell’s shape, capacity and the 2n² shell total.

Titrate di- and triprotic acids (H₂CO₃, H₃PO₄, H₂SO₄) and watch a buffer plateau and equivalence jump appear for each acidic proton.

Watch monomers chain into a macromolecule — addition growth that opens C=C bonds, versus condensation that ejects a water molecule at every link.

Shine light on a metal: electrons fly off only above a threshold frequency, and brighter light means more — never faster. Einstein’s quantum, live.

Drag a marker across a P–T phase diagram to cross the solid, liquid and gas boundaries, find the triple and critical points, and compare water’s negative-slope melting line with CO₂’s positive one.

A virtual burette over a beaker — drip acid into base and read the curve as it tips through the equivalence point.

A logarithmic ruler tying [H⁺], [OH⁻], pH and pOH together, with everyday substances and indicator colour bands placed along it.

Colour the whole periodic table by any property — radius, ionization energy, electronegativity — and watch the across-and-down trends light up.

Type a chemical formula and see its molar mass and the mass percent of every element, drawn as a live bar/pie breakdown.

Three colored gases share one box — measure how each species hammers the walls and watch Dalton’s law assemble the total pressure from the parts.

Assign an oxidation number to every atom in a formula by the rules, then run a redox reaction to see what is oxidised, what is reduced, and which species are the agents.

Watch water cross a semipermeable membrane toward the saltier side until the column it raises balances the osmotic pressure π = iMRT.

Step through the major mechanism types — addition, SN1/SN2, E1/E2, combustion — watching the curved arrows push electron pairs into products.

Split U-235 into a runaway neutron chain or fuse deuterium and tritium into helium — and watch the energy pour out.

Trace the binding-energy-per-nucleon curve to its iron-56 peak and see why fusing light nuclei and splitting heavy ones both release energy.

Chemically distinct hydrogens ring at their own shift; neighbours split each signal by n+1 and peak area counts protons — read a molecule’s NMR like a structure.

Push cell potential off its standard value: vary ion concentrations and temperature and watch Ecell = E° − (RT/nF)·lnQ respond.

Fill the σ/π/σ*/π* levels of a period-2 diatomic, read off the bond order, and predict whether it is paramagnetic.

Avogadro's number as the bridge: convert mass, moles, particles and gas volume at STP for any substance, and feel the sheer scale of 6.022×10²³.

One solution, every concentration unit at once — molarity, molality, mass %, mole fraction, ppm — then dilute it and watch M₁V₁ = M₂V₂ hold.

Ionize a molecule and watch it shatter — the molecular ion, the base peak, and isotope twins (M+2 for Cl, Br) plot a structure from its fragments.

Pick a balanced reaction and the moles of each reactant, watch them drain into product, and read off the limiting reagent, the leftover excess, and theoretical & percent yield.

Tally valence electrons, place bonds and lone pairs to satisfy the octet, and read off the formal charges on every atom.

Stress the Haber ammonia equilibrium — add gas, compress, heat — and watch it shift to counteract you, then re-establish.

Measure pressure from the molecules slamming the walls and watch it match P = (N/A)·⟨KE⟩ — macroscopic pressure built from microscopic chaos.

Why is chlorine 35.45? Mix an element’s isotopes by natural abundance and watch the weighted-average atomic mass and mass-spectrum fall out.

Same formula, different molecule — flip between structural isomers and stereoisomers (cis/trans, enantiomers) in rotatable 3D.

Bonds are springs — each absorbs infrared at its own wavenumber; read a molecule’s transmittance fingerprint and watch the band that owns each dip vibrate.

Strip electrons one by one — the giant jump where the cost explodes is the moment you break into the noble-gas core.

See how the cation/anion radius ratio selects the crystal structure — rock salt, caesium chloride, zinc blende or fluorite — and the coordination it dictates.

Watch an atom shed or grab electrons to reach a noble-gas core — then line up the isoelectronic series and see radius shrink as protons pile on.

Switch between London dispersion, dipole–dipole and hydrogen bonding and watch stronger attractions cluster the molecules and raise the boiling point.

Three diagnostic plots — [A], ln[A] and 1/[A] vs t — reveal the order by which one comes out straight, and read k off its slope.

Lock one variable and vary the rest in a piston of bouncing molecules — watch PV = nRT hold itself together.

Grow a carbon chain, set each C–C bond to single/double/triple, and watch hydrogens auto-fill to valence 4 with the right sp³/sp²/sp geometry.

Mix one s and up to three p orbitals into sp, sp² and sp³ hybrids and see the linear, trigonal and tetrahedral geometries they force.

Flip and scale tabulated step reactions until they sum to your target, and watch their enthalpies add up to the overall ΔH through an energy cycle.

Dissolved gas tracks its partial pressure (C = kH·P) — pop the cap on the soda and the supersaturated gas fizzes out in a storm of bubbles.

Pour heat into a substance at a steady rate and watch temperature climb, then stall flat at each phase change while latent heat breaks the bonds.

Compute a reaction enthalpy as Σ ΔH°f(products) − Σ ΔH°f(reactants) from a stored table, with a bar breakdown of every contribution.

Set ΔH and ΔS, sweep temperature, and find where ΔG = ΔH − TΔS crosses zero — the exact line between a spontaneous reaction and one that runs backward.

Combine reactant gases by the volume ratios their coefficients demand, find the limiting gas, and read off the product volume at any temperature and pressure.

Boyle, Charles, Gay-Lussac, Avogadro — pick a law, sweep its variable, and watch the proportionality trace itself out while the other quantities stay pinned.

Wire two half-cells through a salt bridge and watch electrons flow anode→cathode while E°cell falls out of the standard-potential table.

A zoo of the organic functional groups — each drawn as a skeletal structure with its R–X formula, a real example, and the reactivity it confers.

Heat a metal salt and its electrons jump and fall — each cation paints the flame its own colour, the macroscopic echo of one bright emission line.

Live ICE tables: set initial concentrations and K, solve the equilibrium extent x, and convert Kc to Kp.

Type a reaction and get the smallest whole-number coefficients, the conserved-atom check, and the limiting reagent.

Watch the Michaelis–Menten saturation curve emerge, read Km and Vmax off it, and see how competitive and non-competitive inhibitors bend the Lineweaver–Burk plot.

Pull the partition and watch a gas spread to fill its volume — entropy rising because there are simply far more ways to be spread out than packed.

Drag the reaction enthalpy and activation barrier to read off forward and reverse activation energies — and watch a catalyst carve the hill down.

From percent composition (or raw masses) to the empirical formula: divide by atomic masses, take the mole ratio, scale to whole numbers — then the molecular formula from a measured molar mass.

Every element’s fingerprint of light — bright emission and dark absorption lines for H, He, Ne, Na and Hg on a 380–700 nm strip.

Pauling electronegativity across the whole table, plus a bond predictor — pick two atoms and ΔEN tells you nonpolar, polar, or ionic.

Fill any atom electron by electron — Aufbau order, Hund’s rule and Pauli exclusion drawn as orbital box diagrams.

Drive a non-spontaneous reaction with an external supply and watch Faraday’s laws plate metal: mass = ItM / nF.

Slater’s rules made visible — count how much each inner electron screens the nucleus, then read the net pull Zeff a chosen electron actually feels.

Type a DNA sequence and watch the antiparallel double helix assemble in 3D — A–T held by two hydrogen bonds, G–C by three.

Add up the bond dipoles of a molecule as vectors — watch symmetric shapes like CO₂ and CCl₄ cancel to zero while H₂O and NH₃ do not.

Graham’s law made visible — two gases mix by diffusion while the lighter one races through a pinhole faster, at a rate proportional to 1/√M.

Build the four common metallic unit cells — simple cubic, BCC, FCC and HCP — and read off atoms per cell, coordination number and packing efficiency.

Rusting as electrochemistry: iron oxidising at anode patches under a water film — and how a sacrificial metal flips the cell to protect it.

Rotate about a C–C bond through staggered and eclipsed forms — Newman projection, torsional-energy curve, and the cyclohexane chair↔boat flip.

Le Chatelier on aqueous equilibria — add a shared ion and watch a weak acid stop ionizing or a salt stop dissolving.

Burn an organic compound and weigh the CO₂ and H₂O it produces — back out the moles of carbon, hydrogen and oxygen, then the empirical formula.

A collision reacts only with enough energy AND the right orientation — tally effective hits while the Maxwell–Boltzmann tail grows with temperature.

Dissolve a solute and watch the boiling point rise and the freezing point fall along a phase line — ΔT scales with particle molality, not identity.

Stack close-packed sphere layers ABAB or ABCABC to build HCP and FCC — and find the tetrahedral and octahedral holes hiding between them.

Polar sticks, non-polar runs — watch a mixture split into bands on a TLC plate as solvent climbs, and read each component’s Rf straight off the plate.

A tetrahedral stereocenter beside its non-superimposable mirror image — assign R/S by CIP priority and watch enantiomers rotate polarised light in opposite directions.

Watch forward and reverse rates converge as concentrations level off and the reaction quotient Q climbs to meet K.

A catalyst opens a lower-Ea pathway: compare the two energy profiles and watch the catalysed reactor finish first while the catalyst comes out unchanged.

Measure the surviving ¹⁴C in a sample and read off its age from the 5730-year decay clock with t = (t½/ln2)·ln(N₀/N).

Mix a hot and a cold sample and let q = mcΔT find the shared final temperature — energy lost by one equals energy gained by the other.

Mix a weak acid with its conjugate base, then add strong acid or base and watch pH resist change until the buffer capacity runs out.

X-rays reflect off crystal planes and interfere — watch the path difference 2d·sinθ pass through whole wavelengths and a diffraction peak appears.

Estimate a reaction’s ΔH from a bond-energy table: energy in to break bonds, energy out to form them, and the exo/endothermic balance.

Walk through covalent, polar, ionic, metallic and hydrogen bonds — each a live 3D diagram you can rotate.

Quantized hydrogen — jump an electron between shells and watch it emit or absorb a photon of exactly the right colour.

A = ε·b·c — shine light through a cuvette, build a calibration line from standards, then read an unknown’s concentration straight off the absorbance.

Compare battery chemistries side by side — Daniell, alkaline, lead-acid, Li-ion, fuel cell — their half-reactions, voltage and energy density.

Why atoms shrink across a period and swell down a group — radius plotted against Z with the nucleus pulling its outer shell inward.

Sample the hydrogen wavefunction |ψₙₗₘ|² as a glowing 3D point cloud and rotate the real shapes of s, p, d and f orbitals.

Vary temperature and activation energy in k = A·exp(−Ea/RT); read the rate constant off a straight ln k vs 1/T line and the Boltzmann tail.

Rotate diamond, graphite, graphene, fullerene C60 and the nanotube — same atom, wildly different structures, hardness and conductivity from sp³ vs sp² bonding.

Build a branched carbon skeleton and watch the IUPAC name assemble itself — locants, di/tri prefixes, alphabetical order, and the lowest-locant rule.

Three lenses on one reaction — Arrhenius, Brønsted–Lowry and Lewis — highlighting the proton transfer, conjugate pairs, and electron-pair donor/acceptor.

Weak-acid dissociation HA ⇌ H⁺ + A⁻: compute pH and percent dissociation, and see why dilution raises it (Ostwald).

把两个元素放进聊天室，让它们真实的化学性质来书写对话。碱金属调情，卤素占有欲爆棚，惰性气体对谁都已读不回——而电负性差决定了它们是成键、共享还是爆炸。