Classes of Crystalline Solids — Overview & Examples

Crystalline Solids

There are three phases of matter: solid, liquid, and gas. Solids are distinguished by a defined shape and closely packed atoms. Among solids there are different types:

• Metallic: hard metals elements like iron or alloys like bronze.

• Amorphous: soft solids like plastics and rubber.

• Crystalline: materials that form crystal lattices like sugar and sodium chloride (table salt).

Crystalline solids are distinctive from amorphous solids. Amorphous solids have disorganized particles throughout. Crystalline solids have highly organized structures that persist throughout the whole substance. The ions, molecules, or atoms within a crystal maintain a repeated pattern that causes distinct visible shapes.

Types Of Crystalline Solids

Crystals can be classified into different types of crystalline solids.

• Ionic: the particles that make up these crystals are ions. A common example is table salt (NaCl).

• Molecular: the particles making up the crystal consist of molecules. These molecules experience Van der Waal's forces. So, they are held together by dispersion, dipole-dipole interactions, or hydrogen bonding. A great example is ice. The H$_2$O molecules are held together by water's hydrogen bonding.

• Covalent Network: atoms within this solid interact through covalent bonds in a 3D arrangement. An example is diamond which is made of networks of carbon.

• Metallic: these are solids with metallic properties. They are made of large networks of atoms. Silver and tin are examples.

(Video) Ionic Solids, Molecular Solids, Metallic Solids, Network Covalent Solids, & Atomic Solids

by The Organic Chemistry Tutor

In this video, The Organic Chemistry Tutor walks you through crystalline solids. He starts with ionic solids, which have ionic bonds between metal and nonmetal ions. The ion's electrostatic interactions generate massive melting temperatures. The Tutor reminds us that the melting point correlates to the ionic charge, lattice energy, and atomic radius. Next, he explains molecular solids. They're held together by Van der Waal's forces. So they have much lower melting points. Subsequently, he presents the atomic solids. Atomic solids are the broadest category. They include metals, noble gases, and network covalent compounds. The properties of the network covalent compounds depend on the allotrope. Finally, he presents five practice problems that could appear on a test. Do you need a deeper understanding of crystalline solids? This video can help!