Solids and Crystal Structure
Crystalline solids have particles in repeating patterns.
About this topic
Solids may be crystalline, with particles in a regular repeating pattern, or amorphous, without long-range order, like glass and plastic. Crystalline solids are classified as ionic, covalent network, metallic or molecular, and have sharp melting points. The smallest repeating unit of a crystal is the unit cell, such as simple cubic, body-centred cubic or face-centred cubic.
The type of particle and the forces between them decide properties. Ionic crystals like salt are hard and brittle; covalent networks such as diamond are extremely hard; metals conduct and are malleable; molecular solids such as ice and sugar are soft with low melting points. Amorphous solids soften over a range of temperatures rather than melting sharply, since their bonds differ in strength. Crystals break along flat planes related to their internal arrangement, which is why gemstones have flat faces.
Example: when you see salt crystals under a magnifier they look like tiny cubes, which reflects the cubic arrangement of Na+ and Cl- ions. Snowflakes are six-sided because of the hexagonal arrangement of water molecules in ice. X-ray diffraction is used to determine crystal structures, as in the discovery of the DNA double helix.
A misconception is that glass is a slow-flowing liquid; it is an amorphous solid.
Key ideas
- Ionic, molecular, metallic, covalent network
- Amorphous solids lack order
- Unit cells repeat
Quick check
Use cases: where Solids and Crystal Structure helps
- Homework: review the key idea behind Solids and Crystal Structure before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Solids and Crystal Structure without notes.
- Visual learning: play with the interactive lab to see how Solids and Crystal Structure changes when you adjust its inputs.
- Teaching a friend: explain Solids and Crystal Structure in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Solids and Crystal Structure?
Crystalline solids have particles in repeating patterns.
What will I learn in Solids and Crystal Structure?
Ionic, molecular, metallic, covalent network. Amorphous solids lack order. Unit cells repeat.
Is Solids and Crystal Structure part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Solids and Crystal Structure lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Solids and Crystal Structure?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.