The Eka Cards

LITIn 1871 Mendeleev left gaps in his table and named the missing elements with Sanskrit "eka" (one): eka-aluminium, eka-boron, eka-silicon. Gallium (1875), scandium (1879) and germanium (1886) filled them. Each card: his prediction, typed against the measured value. Tap a card to run his method yourself on the panel below.

MODELThe neighbour method. Mendeleev estimated a gap from its four neighbours (above, below, left, right). Pick a gap; the estimate emerges as the average of the four, compared live with the real value.

gap: Gegap: Gagap: Segap: Snhide a random element

Sources: D. Mendeleev, Liebigs Annalen Suppl. 8 (1871); standard comparison tables (e.g. Scerri, The Periodic Table, OUP 2007/2020). Modern values: CRC Handbook. Predicted figures are the commonly cited ones; minor variations appear between secondary sources.

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