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Why the Towers Fell
The Structure of Metal

Diagram of metal crystal structure during bend

A metal is comprised of many individual crystals, or grains. These crystals are held together by electrons in the same way that electrons hold the atoms within each crystal together. For more on this type of bond, see Metal Basics.

An important characteristic of metal is its ability to bend. Here are two metal crystals side by side. Notice how their atoms shift to produce a bend.

This is a simplified example that shows how crystals can change shape to allow metal to bend. In a real metal, crystals contain many more atoms and many dislocations (extra planes of atoms), and they are surrounded by many other crystals that can also alter their shapes.

Note: Although the crystal above is depicted in two dimensions, imagine that there are many layers of similarly arranged atoms behind this top layer, creating a three-dimensional, cubic structure.

To continue to the next section, select Heat.

Metal Basics | Move | Slip | Bend | Heat

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