The crystal structure of sodium chloride

The crystal structure of sodium chloride - + ions The...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
The crystal structure of sodium chloride The unit cell of sodium chloride is cubic, and this is reflected in the shape of NaCl crystals The unit cell can be drawn with either the Na + ions at the corners, or with the Cl - ions at the corners. If the unit cell is drawn with the Na + ions at the corners, then Na + ions are are also present in the center of each face of the unit cell If the unit cell is drawn with the Cl - ions at the corners, then Cl - ions are are also present in the center of each face of the unit cell
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Within the unit cell there must be an equal number of Na + and Cl - ions. For example, for the unit cell with the Cl - ions at the center of the faces The top layer has (1/8+1/8+1/8+1/8+1/2)=1 Cl - ion, and (1/4+1/4+1/4+1/4)=1 Na + ion The middle layer has (1/2+1/2+1/2+1/2)=2 Cl - ions and (1/4+1/4+1/4+1/4+1)=2 Na
Background image of page 2
Background image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: + ions The bottom layer will contain the same as the top or 1 each Cl-and Na + ions The unit cell has a total of 4 Cl-and 4 Na + ions in it. This equals the empirical formula NaCl . Close packing of spheres Many ions are spherical and many small molecules pack in a crystal lattice as essentially spherical entities. Spheres can pack in three-dimensions in two general arrangements: Hexagonal close packing Cubic close packing The coordination number is the number of particles surrounding a particle in the crystal structure. In each packing arrangement above (hexagonal close pack, cubic close pack), a particle in the crystal has a coordination number of 12 The NaCl (face centered cubic) has a coordination number of 6...
View Full Document

Page1 / 3

The crystal structure of sodium chloride - + ions The...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online