AN IONIC BONDING LAB

electronbalance.

Move electrons. Discover what holds atoms together.

Choose your difficulty

8 problems per difficulty. Challenging draws a random set every time you choose a new set.

Best run: —

Try freely. Undo is always there.Your progress is saved on this device.

0pts

First connection

Move outer electrons. Charge = protons − electrons.

0 / 2 stableCharge 0 neutral28 conserved e−Time 00:00.00Best —
Electron Transferred Stable Ionic attraction
0 transfers
Drag a nucleus to move its atom.SIMPLIFIED BOHR MODEL

Easy puzzles

Your progress0 / 8

Progress saved on this device
A LITTLE EXPLORATION GOES A LONG WAY

Find a stable balance.

Connect the dots to the chemistry. Under each atom, p⁺ counts protons and e⁻ counts electrons. Subtract electrons from protons to find the charge; the highlighted electron counts change when you transfer an electron. Your first loss and gain examples offer a brief prediction. After moving the electrons, build the simplest formula to finish the puzzle and earn a 50-point bonus. Changing a count updates its charge immediately. Correct mistakes and try again; the bonus stays available. Formula work is untimed, and predictions do not affect your score.

  1. Move an electronDrag a dot on an outer shell to another atom. Or tap an outer dot, then tap the receiving atom. Atoms hold still while you choose.
  2. Watch what changesLosing electrons makes an ion positive (+). Gaining electrons makes it negative (−).
  3. Look for stable shellsGreen means a noble-gas configuration: 2 electrons in the first shell, or 8 in the outer shell for these ions. The ion charges must also form a valid compound.
Choose your challenge. Each difficulty has eight unique compounds. Easy uses two atoms, Medium uses three, and Challenging uses four or five with larger charge ratios and mixed-metal compounds. Compounds do not repeat across difficulties. You need to balance every atom. Solve puzzles to unlock the next one in that difficulty. Open the level picker to change difficulty.

Make room to experiment. Drag a nucleus to reposition an atom. Pause motion whenever you like.

Experiment freely. Undo and Reset are always available. Earn 100 points for each level, plus 50 for a shortest solution and 50 for the correct formula. Each difficulty keeps its own progress and scores; retries never subtract points.
Keyboard controls & model notes

Tab to an outer electron and press Enter or Space. Tab to a “Give electron to…” button and press Enter or Space. Escape cancels selection. Undo restores the previous move and transfer count.

Only outer electrons move. This simplified model keeps at least one electron per atom and limits each atom to its starting set of shells (up to 20 electrons). A full shell does not make every ion chemically valid.

The total charge starts at zero and stays zero because every electron is conserved. A puzzle also requires stable, chemically valid ions. Completed levels are saved on this browser; an unfinished puzzle restarts when you reload.

Ionic solids form repeating three-dimensional crystal lattices. The completion sketch illustrates attraction and repetition, not the exact crystal structure or isolated molecules.

Glowing links show attraction between positive and negative ions. Each ion can attract several neighbors, forming a repeating crystal lattice.

Chain your bonds. Create a new glowing link on consecutive electron transfers to build a 2×, 3×, or higher BOND COMBO! Each bond-forming move counts once, even if several links appear. Take your time between moves. A transfer with no new link or Undo ends the streak; Reset, Try again, and a new puzzle start fresh.

Random challenges, real chemistry. Challenging draws eight different compounds: two four-atom puzzles, four larger-ratio puzzles, and two mixed-metal puzzles. All use 4–5 atoms, balanced ion charges, and 3–6 electron transfers for a shortest solution. Atom order is shuffled too. Open the puzzle picker and choose New random set to redraw. Reset and Try again keep the same puzzle. Time records and points follow the compound across sets, so replays cannot farm points.

Keep going in Endless. Solve unlimited random 4–5 atom challenges. Each solve earns 100 run points, plus 50 for a shortest solution without Undo or Reset and 50 for the correct formula. Every challenge scores once. Continue to earn more; completed challenges cannot be retried in the same run. Undo and Reset remain available before solving, and keep all time spent. Open the Endless counter to pause or End & save run. Runs resume after reloading, including your current atoms and moves. Scores, times, transfers, and best combos are saved on this device; Run history lets you export them.

Race your own record. The timer starts when a puzzle opens and stops on the final correct transfer. Menus and hidden tabs pause the clock; Pause motion only stops the atoms. Try again starts a fresh attempt. Undo keeps the time already spent. Your latest time and personal best are saved for each level. Beat a previous time to earn NEW RECORD!

How the forces work

Every ion feels the combined electrical force from all other ions. Opposite charges attract; like charges repel. Twice the charge means twice the force. Twice the distance means one-quarter the force. Lighter ions accelerate more under the same force.

This is a scaled, two-dimensional Coulomb model. Invisible diagram bumpers and screen walls keep atoms readable; they do not represent real ionic sizes or crystal structure. Real atoms also involve quantum effects and three-dimensional surroundings.

Endless runs

100 points per solve · +50 for a shortest solution without Undo or Reset, plus 50 for the correct formula.

Enter your initials in High scores to join the live board.

Recent runs

ENDLESS / WORLD BOARD

ONE MORE COMPOUND.

HIGH SCORES

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Enter your initials. Solve a formula.
Put your score on the board.

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Initials and scores are public. Your best run takes one spot. No account needed.

BONDS × CHAIN + 100 SOLVE + 50 SHORTEST + 50 FORMULA

 PREDICT → TRY → EXPLAIN

Predict a charge.

Choose, then move an electron to test your idea. Predictions do not affect your score. The timer is paused here.