The brittleness or flexibility of a compound depend son how easy it is to shift atoms around in their positions in the lattice.

In covalent networks this is nigh impossible because many, many covalent bonds need to be broken. For this reason covalent networks are very brittle and tend to shatter, rather than bend.

Molecules, on the other hand, are not strongly held in their lattice positions. Being fixed to each other only by the weaker intermolecular forces, they are easily shifted. How brittle is a candle? How brittle is vegetable oil?

Metals are cations sitting in a lattice bathed in electrons. If a whole row of copper ions is pushed along by one place,the overall structure of the lattice is hardly disturbed. This is why metals bend much more easily than ionic compounds or covalent networks, and areso (relatively) easily flattened or drawn out into wires.

Ionic compounds are doubly cursed. As in covalen tnetworks many, many bonds need to be broken to shift the lattice. On top of this, unlike metallic substances, if such a shift (being pushed along one place) occurs, positive ions line up against other positive ions and negative line up against negatives leading to electrostatic repulsion. Ionic compounds typically shatter under stress.

Close window to continue.