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Drag particles. Protons and neutrons go in the nucleus; electrons snap onto the shells (2, 8, 8 max). Try making Carbon, then Na⁺ by removing an electron.
Make your own cards One per line. Use Term: definition, Question | answer, Term - definition, or just a sentence and I will blank out a key word. Paste lines from your own notes or the PMT definition sheets.
Each topic has key points followed by in-depth notes with worked examples, exam tips and common mistakes. Use the find box to jump to a word, and the PMT links for past-paper questions. Display, spacing and font options are in the ⚙ settings.
How it works
Bond: tap one atom, then another (or drag between them). Tap the same pair again for a double, then a triple bond. Move: drag atoms around. Lone pair: tap an atom to add a pair.
Drag the 3D view to rotate
Bond angle rules (VSEPR)
Electron pairs (bonding or lone) repel, so they sit as far apart as possible.
A double or triple bond counts as one electron domain.
Repulsion: lone pair–lone pair > lone pair–bonding pair > bonding pair–bonding pair, so each lone pair squeezes the bond angle by about 2.5° (CH₄ 109.5° → NH₃ 107° → H₂O 104.5°).
With 5 domains lone pairs go equatorial (more room); with 6 they sit opposite each other.
2D key: plain line = in the plane of the page, solid wedge = towards you, dashed wedge = away from you. Yellow dots = bonding pair, blue dots = lone pair. Teal squares in 3D = planes the atoms lie in.
How it works
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