⏱️ 3 min read
October 29, 2020
In AP Chemistry, you learn about 3 main states of matter: solids, liquids, and gasses. While liquids and gasses are certainly important, in this article we're going to be discussing solids and the 4 types of solids that you will have to be able to identify on the AP Chem exam. There are 4 major types of solid: molecular, covalent network, ionic, and metallic. Let's dive in!
Molecular solids are made of molecules or atoms held together by intermolecular forces, not covalent bonds.
Intermolecular forces are weaker than ionic or covalent bonds, so molecular solids are relatively soft and flexible.
Covalent network solids are held together by covalent bonds in a large network.
Source: Science Media Group
They are usually hard and brittle.
Ionic solids are made up of oppositely charged ions held together by electrostatic attraction (a.k.a. ionic bonds).
Electrostatic attraction just describes the attractive force between a positive charge and a negative charge.
The strength of an ionic solid can be described by Coulomb's Law (Q = k(Q1Q2/r^2))
Essentially, high charge + small ions = high electrostatic force
The ions form a crystal lattice structure, seen in NaCl below:
They're hard and brittle.
Metallic solids are metal atoms held together by metallic bonds.
Metallic solids vary a lot when it comes to melting points. Tungsten has the highest melting point at 3422°C, whereas mercury has the lowest at -38.83°C.
Congratulations! You now know about the properties of the 4 major types of solids in AP Chemistry. In applying this knowledge on the exam, you will be asked to identify a solid by its properties. For example, if I were to ask you what type of solid a compound was if it was brittle, melted at 1500 degrees, and conducted electricity when dissolved, you should know that this is an ionic solid. There are tons of practice questions out there just like this. Good luck!
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