Chemistry / Chem 1493 · Procedure · 60–90 seconds
Computing a Metal's Density from Its Unit Cell
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Computing a metal's density from its unit cell means finding the mass of the particles belonging to one unit cell from their count and molar mass, finding the unit cell's volume from its edge length cubed, and dividing the first by the second.
Calcium crystallizes face-centered cubic with an edge length of 558.8 pm. Its unit cell holds four calcium atoms, giving a cell mass of about 2.66 × 10⁻²² g; the cell volume, (558.8 pm)³, is about 1.745 × 10⁻²² cm³. Dividing gives a calculated density near 1.53 g/cm³, matching calcium's known density.
Leaving the edge length in picometers instead of converting to centimeters before cubing it for volume produces a density wrong by many orders of magnitude, not a small error.