Close Packing, Unit Cells and Ionic Lattice Types · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

One small block, repeated

Science · Chemistry · ages 21-22
Name ______________________   Date ____________

  1. How many atoms does a face-centred cubic cell hold?

    • 1
    • 2
    • 4

  2. A corner atom is shared by eight cells. How much counts toward one cell?

    • One whole atom
    • One half
    • One eighth

  3. An atom on a cell face counts as one half toward that cell.

    Circle one:   True   False

  4. How do you get the density of a crystal from its unit cell?

    • Cell volume divided by cell mass
    • Mass of the atoms in one cell divided by the cell volume
    • Cell edge multiplied by atom count

  5. A body-centred cubic cell has eight corner atoms and one centre atom. How many atoms does it hold? Type the number.

    Answer: ______________

  6. What decides the named structure type of a packed ionic solid?

    • The colour of the larger ion
    • Which gaps between packed atoms get filled
    • The speed of crystal growth

  7. Two crystals pack the same spheres but stack their layers in different repeating orders. What are they?

    • Hexagonal and cubic close packing
    • Simple cubic and body-centred cubic
    • Metal and insulator

  8. A radius-ratio prediction gives the wrong coordination number. What might explain it?

    • The bonding is far from purely ionic
    • The cell edge was measured twice
    • The ions touch too neatly
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Answer key

For grown-ups. Fold this page away before handing over the rest.

One small block, repeated W1-mt_LzpVzwrDm3-s1

  1. 4 · Eight corners give one atom and six faces give three more, making four.
  2. One eighth · Divide the atom among its eight cells: each cell claims one eighth.
  3. True · The face is shared by two cells, so each claims one half.
  4. Mass of the atoms in one cell divided by the cell volume · Density is mass over volume, applied to a single repeating block.
  5. 2 · Eight eighths make one, plus the centre atom makes two.
  6. Which gaps between packed atoms get filled · Each pattern of filled gaps has its own name.
  7. Hexagonal and cubic close packing · The layer order is exactly what separates the two close packings.
  8. The bonding is far from purely ionic · Size comparison assumes simple ionic packing, and real bonding breaks that picture.
Worksheet · LightMySky