# Three A4 aids · complete text and tactile routes

Original SVG and matching one-page **A4 210 × 297 mm** selectable-text PDF are linked below. The PDFs are **untagged**, so the full text on this page is the reliable screen-reader route. Number, word and reading order carry meaning without colour. Print at actual size, cut full-word cards, add a raised line or spacer if useful, or read the words aloud. A tactile route here is a **paper arrangement**, not a specialist-tested tactile graphic.

## [Atom model and its limits](atom-model.svg) · [PDF](atom-model.pdf)

Top statement: “A picture can show parts; it is not a measured path.” A schematic central **NUCLEUS** contains positive protons (`p+`) and neutral neutrons (`n0`). Outside, negative electrons (`e−`) are represented on **energy level 1** and **energy level 2** rings. These rings/dots are a convention, **not circular electron tracks**. The drawing is not to scale, does not identify a particular element, and does not give actual electron positions, paths or particle counts. Bottom words: positive protons and neutral neutrons—nucleus; negative electrons—represented in energy levels outside; counts require Z, A and charge. Tactile route: stack a central “nucleus / protons positive / neutrons neutral” card, an “electrons negative / outside” card, then two *numbered* energy-level cards; place a raised “model, not measured path” strip across the whole set. Do not imply the raised curves are physical trajectories.

## [A, Z and charge count mat](count-mat.svg) · [PDF](count-mat.pdf)

Read in order. **GIVEN:** element/name, integer A, integer Z, charge q in elementary-charge units. **DERIVE:** 1 protons `p=Z`; 2 neutrons `n=A−Z`; 3 electrons `e=Z−q` for the specified monoatomic atom/ion; 4 reverse checks `p+n=A`, `p−e=q`. `2+` means q=+2. Blank charge means neutral **only if the task says so**. Worked neutral example: carbon-12, A12 Z6 q0 → p6, n6, e6; checks 6+6=12 and 6−6=0. A is an integer count for an isotope, not decimal standard atomic weight. Tactile route: four numbered full-word rows plus movable A/Z/q number cards; put counts on the row then read the reverse check aloud.

## [Isotope or ion decision fork](isotope-ion-fork.svg) · [PDF](isotope-ion-fork.pdf)

**Branch 1 · isotope comparison:** neutral carbon-12 Z6 has p6 n6 e6; neutral carbon-13 Z6 has p6 n7 e6. Same element/Z, different neutron count/A: the **nucleus** differs. These cards do not state abundance or radioactivity. **Branch 2 · charge comparison:** neutral magnesium-24 has p12 n12 e12; magnesium-24 2+ has p12 n12 e10. Same isotope/nucleus, different electron count: the **charge** differs. The card does not show a real reaction. Bottom decision order: same Z? same A? same e? Tactile route: make two separate pairs of full-word cards; align proton/neutron/electron counts in three columns and mark the changed column with a raised token. The words “nucleus differs” or “electron count differs” remain attached.

The source examples are explained in [original model cards](../MODEL-CARDS.md), with [rights](../SOURCE-AND-RIGHTS.md) separate from the [DejaVu font notice](FONT-RIGHTS.md).