UNIT 2.3 STRUCTURE OF IONIC SOLIDS

STRUCTURE OF IONIC SOLIDS

Using the last subunit (2.2) we now look at the structure of ionic solids.  The cations (positive particles) and anions (negative particles) will arrange themselves so that they minimize the repulsive force and yet maximize attractive force.  This gives them a geometry we call a lattice.  

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A lattice is a recurring pattern in the crystals that grow.  I introduced this in Chemistry 1 but now we will look at the types of lattices.

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As I don't draw well, and why recreate something somebody else did way better, do a search for 'types of lattice structures chemistry' and you can see all the different types of bonds.  But we will go over a few.

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Cubic:  This I have a model of sitting in my room.  You can see the 2 different types of atoms in a 3D structure.  It is as simple as it gets: a cube with the different atoms in each corner.  NaCl is a great example of this.  Large salt crystals will actually grow cubic, just like the molecular lattice.

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Body centered cubic: Add a single atom in the center of the cubic.  

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Face centered cubic: Add atoms at each center square of the cubic (6 additional atoms total)

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I have shown a blue crystal of Cu(II)SO4 before.  It is actually orthorhombic.  Look it up.  Are the lengths of the lattice equal?  

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