Name: States of Matter
Uploaded: 2019-07-19
Duration: 7 min 38 s
Description: The Earth is composed of matter which is found in three different states. Watch this video to learn about these three states and their similarities and differences.

Question

Explain the following: why are most metals strong, but ionic solids are brittle?

Accepted Answer

Ionic crystals may split apart when hit in the same direction as the layers of ions. The layers of ions may be displaced by the force of the blow so that ions with the same charge come together. The repulsions between thousands of ions in the layers, all with the same charge, cause the crystal to split along these cleavage planes. Hence, ionic solids are brittle.

A metallic lattice consists of ions surrounded by a sea of electrons. The ions are often packed in hexagonal layers or in a cubic arrangement. When a force is applied, the layers can slide over each other. But in a metallic bond, the attractive forces between the metal ions and the delocalised electrons act in all directions. So when the layers slide, new metallic bonds are easily re-formed between ions in new lattice positions and the delocalised electrons. The delocalised electrons continue to hold the ions in the lattice together. The metal now has a different shape. This explains why metals are malleable (they can be hammered into different shapes) and ductile (they can be drawn into wires). The high tensile strength and hardness of most metals are also due to the strong attractive forces between the metal ions and the delocalised electrons. Hence, most metals are strong, but ionic solids are brittle.

Explain the following: why are most metals strong, but ionic solids are brittle?

Important Questions on States of Matter

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