Understanding Type Three Molecular Compounds
Type three compounds are molecular compounds formed between two nonmetals, unlike type one and type two ionic compounds which involve metals and nonmetals. These compounds require a specific naming system using Greek prefixes to indicate the number of atoms of each element.
Greek Prefixes for Molecular Compound Naming
To name these compounds, you must memorize Greek prefixes that denote numbers:
- Mono = 1
- Di = 2
- Tri = 3
- Tetra = 4
- Penta = 5
- Hexa = 6
These prefixes are essential for naming binary molecular compounds (compounds with two different nonmetal elements).
Naming Binary Molecular Compounds: Step-by-Step
The general formula for naming is: [Prefix] + Name of First Element + [Prefix] + Base Name of Second Element + "-ide"
Example: N2O5
- Count atoms of the first element (Nitrogen): 2 → prefix "di"
- Write the first element name: "nitrogen"
- Count atoms of the second element (Oxygen): 5 → prefix "penta"
- Use the base name of oxygen: "ox"
- Add suffix "-ide" to form "oxide"
- Combine: dinitrogen pentoxide
Note: When two vowels meet (like "a" and "o"), the first vowel is often dropped for easier pronunciation (e.g., "pentaoxide" becomes "pentoxide").
Important Exceptions and Rules
- The prefix "mono" is never used for the first element. For example, CO is "carbon monoxide", not "monocarbon monoxide".
- When the second element’s prefix ends with a vowel and the element name starts with a vowel, the vowel in the prefix is dropped (e.g., "monoxide" not "monooxide").
- The base name of the second element is derived by removing the ending of the element name and adding "-ide" (e.g., chlorine → chloride, oxygen → oxide).
Additional Examples
- SCl2: Disulfur dichloride
- NO: Nitrogen monoxide (not mononitrogen monoxide)
- SeF6: Selenium hexafluoride (no "mono" for selenium)
Molecular vs Ionic Compounds
Unlike ionic compounds, molecular compounds do not form ions but exist as molecules. For example, N2O5 is a molecule, not a lattice of ions. This distinction is important for understanding why naming conventions differ.
Summary
- Use Greek prefixes to indicate the number of atoms in molecular compounds.
- Do not use "mono" for the first element.
- Modify prefixes when vowels meet for easier pronunciation.
- Use the base name plus "-ide" for the second element.
- Practice with examples to master naming molecular compounds.
Related Resources
For further reading on related topics, check out these guides:
Right now we learned about ionic compounds metal and non-metal. There are two types, type one and type two. Type
one has only one type of ion for the metal. Type two has more than one type of iron for the metal. There are another
type of compounds called type three compounds. Basically you get type three compounds from non-metal and non-metal
bonding. When non-metal element make a compound with nonmetal, you make type three compounds. Now we are learning
about naming namings of compounds. For naming for these molecular compounds we need to learn something called prefaces.
Greek prefaces. This is something you have to remember. It will need some practice. You have to know mono means
one di means two. Try three. Tetra penta hexa like that you should know the meaning of
those Greek prefixes. We have to study that one. And we need that information to name this non-metal and non-metal
compounds. Let's see how we are going to use it. I'm going to skip this one because let's go to example then it's
going to be much easier to understand. It says binary molecular compounds with two nonmetals. Binary means actually
two. And let's try to name this. I'll just go over very brief. It says preface name of the first element preface base
of the second element plus ID. What does that mean? So let's try the name of N205 using this formula. First we have write
the preface. You can see there are two nitrogens here in N2. First preface belongs to the first element is two. Two
means die in the prefaces. First I will write D. Then I have to write the name of the first element. First element is
nitrogen. I will write the nitrogen. Then we have another preface that is for the second element. So the second
element we have five oxygen. Five means penta. I will write penta. Then the base name of the second element plus ID. What
does that mean? Second element is we know oxygen and but we don't need the name of the element is say the base name
base name is ox. If you remember that when we are learning about all the compounds chloride the base name is
chloro fluide. For fluoride the base name is flow just like that base name of oxygen
is ox. Then we have tried oxide. Basically this is same like the ion 2 minus is oxide. But please understand
there are no ions here. There are no ions here. This is a molecule. What does that mean? Because this is a nonmetal.
This is a nonmetal. It is not ionic. It behaves like a molecule. That means just like hydrogen. I told you another
example. If you have a balloon of hydrogen and if you zoom it and zoom it and zoom it in, you will see two
hydrogen atoms together. But in sodium chloride which is an ionic compound they are always attached to different cations
and annions like a latis big giant latice there are no such thing as molecules in ion here what I'm trying to
say is even though we say di nitrogen penta oxide basically we write the name of the anion there are no annions here
it is just a form of representation according to this this is the name but the correct way is not exactly whenever
We see two wows you know wow a e i o u two wow together we combine them. In this case we do not say di nitrogen
pentto oxide we just remove a and we write pentoxide x i d pentoxide di nitrogen penttoxide for this one let's
see2 how do we write it as a fresh even without knowing this is a nonmetal
chlorine is a nonmetal it is a molecular compound when you are writing nonmetals and nonmetals this is the way we have to
use we will write two means di then name of the first element sulfur s u L F U R sulfur then again write D C H L O R I D
E just like the name of the annion usually we write these dice together dulf dchloride next one how do we write
first start with what d nitrogen now we have how many oxygen are there one one we have to write monorite mono oxide now
again we have a exception because there are two O's here we don't write two O's we write only one know we say monoxide
we just get rid of one just like we don't say pent oxide we say penttoxide just like that we don't say monoxide we
say monoxide next one how would you write a f6 how many selenium are there one when I'm looking at the formula
instruction or whatever I would write mono mono means there's only one selenium right monoselenium monoselenium
there are six florine six means hexa hexa florine is base name and ide just like fluoride Right? So this is the name
we get from this formula. But this is not correct. The reason is I told you that as chemist we have weird thing
about one. Whenever we see one in the first element we don't write mono. Whenever we see mono in the first
section first prefix we don't write it. We write selenium hexaflloride. That is something you have to understand. We
never write mono in the first time. You will understand that in a second when you see this one. The way you have write
from this expression is mono carbon because there's one carbon right and one oxygen also mono for the oxygen oxide
and now we discussed that when there are two O's monoxide we don't say that we say monoxide since it is a mono in the
first element we don't write it we just say carbon monoxide there are certain exceptions just like exception for mono
in the first element we don't write it and also whenever we see monoxide or penttoxide we combine those two and get
rid of one
Heads up!
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