Naming Covalent Compounds
Greek prefixes show the number of atoms.
About this topic
Covalent (molecular) compounds between two non-metals are named using Greek prefixes for the number of atoms: mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona- and deca-. The second element ends in -ide. Examples are carbon dioxide (CO2), dinitrogen tetroxide (N2O4) and phosphorus pentachloride (PCl5).
The prefix mono- is normally dropped from the first element, so CO is carbon monoxide, not monocarbon monoxide. The element listed first is the one farther left or lower in the periodic table. When a prefix ends in a vowel and the element begins with one, the vowel is usually dropped for easier pronunciation, as in tetroxide and monoxide. Prefixes show the actual number of each atom, because the same two elements can form several compounds with different properties.
Compare carbon monoxide, a poisonous gas, and carbon dioxide, which we breathe out and plants take in. Sulfur dioxide and sulfur trioxide are also different, as are nitrogen dioxide and dinitrogen pentoxide. Common names remain, such as water, ammonia, methane and glucose.
Students often use ionic naming rules here, or apply prefixes to compounds with metals. Another mistake is naming acids like molecular compounds; hydrogen chloride gas is HCl, but in water it is hydrochloric acid, which follows its own rules.
Key ideas
- mono, di, tri, tetra
- CO₂ carbon dioxide
- Skip mono on the first element
Quick check
Use cases: where Naming Covalent Compounds helps
- Homework: review the key idea behind Naming Covalent Compounds before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Naming Covalent Compounds without notes.
- Visual learning: play with the interactive lab to see how Naming Covalent Compounds changes when you adjust its inputs.
- Teaching a friend: explain Naming Covalent Compounds 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 Naming Covalent Compounds?
Greek prefixes show the number of atoms.
What will I learn in Naming Covalent Compounds?
mono, di, tri, tetra. CO₂ carbon dioxide. Skip mono on the first element.
Is Naming Covalent Compounds 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 Naming Covalent Compounds 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 Naming Covalent Compounds?
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.