Naming Binary Molecular Compounds: Study with Video Lessons, Practice Problems & Examples

Binary molecular compounds consist of two different nonmetals, such as water (H₂O) and nitrogen oxides (NO). Naming these compounds involves using numerical prefixes: mono (1), di (2), tri (3), tetra (4), penta (5), hexa (6), hepta (7), octa (8), nona (9), and deca (10). The first nonmetal retains its name without "mono," while the second adopts the "ide" suffix. If a prefix ending in 'a' precedes 'o', the 'a' is dropped, as in "tetroxide" for four oxygens. Understanding these rules is essential for accurate chemical communication.

Naming Binary Molecular Compounds Concept 1

Now, binary molecular compounds are molecular compounds that contain 2 different elements together. These elements being nonmetals. For example, we have water, and we have nitrogen with oxygen. Here we have hydrogen with oxygen. That's 2 different elements together. Here we have nitrogen with oxygen. Again, 2 different nonmetals together. Now we're going to say that these molecular compounds utilize numerical prefixes, and that's because these numerical prefixes are always required because these compounds can combine in different proportions. Now with numerical prefixes, we have mono, which is 1, di, which is 2, tri, which is 3, tetra, which is 4, penta, which is 5, hexa is 6, hepta is 7, octa is 8, nona, a little weird sounding, is 9, and then, of course, deca is 10. So just remember when we talk about binary molecular compounds, that's molecular compounds, covalent compounds that contain 2 different, nonmetals together.

Naming Binary Molecular Compounds Concept 2

So when it comes to naming binary molecular compounds, these are the rules you need to keep in mind. So step 1, we're going to say the first nonmetal is named normally and uses all numerical prefixes except for mono. So it doesn't ever use mono. The second nonmetal keeps its base name, uses any numerical prefix, and has its ending changed to "ide". And when naming, if the letter "a" of the numerical prefix is next to a letter "o", we can just drop the letter "a". For example, we say tetraoxide, meaning we have 4 oxygens within our molecular compound. We're going to say here "a" and "o" are next to each other and we're going to do what it says. We are going to drop the letter "a". So tetraoxide would become tetroxide. So keep these steps or rules in mind when naming any type of binary molecular compound.

Naming Binary Molecular Compounds Example 1

In this example question, it says write the formula for each of the following compounds. So for the first one we have is disulfur monochloride. So di means 2 sulfurs. So that's S₂ and then mono means we have one of it, which is chloride. Chlorine is the base name for chloride, and this would be S₂Cl. For the next one, we have tetraphosphorus pentaselenide. Alright, so tetra means 4; therefore, 4 phosphoruses, so P₄. Penta means 5, and selen is the base name of selenium, which is Se. Thus, there being 5 of it, the formula would be P₄Se₅. Then, finally, we have dibromoheptoxide. So di means 2, which refers to 2 bromines, so Br₂. We have heptoxide. So hept comes from hepta, which means 7, and ox represents oxygen, meaning there are 7 oxygens. So dibromoheptoxide is Br₂O₇. So just remember, the first nonmetal keeps its name as normal, uses all numerical prefixes except for mono. The second nonmetal uses any numerical prefixes, but has its ending changed to ide.

Give the systematic name for the following compound:SeF₆

• A. selenium fluoride
• B. selenium hexafluoride
• C. monoselenium hexafluoride
• D. monoselenium fluoride
• E. selenium fluorite

Give the systematic name for the following compound:IO₅

• A. iodine oxide
• B. monoiodine oxide
• C. iodine pentoxide
• D. iodide pentoxide
• E. monoiodide pentoxide

Give the systematic name for the following compound:N₂S₄

• A. nitrogen tetrasulfide
• B. dinitrogen tetrasulfide
• C. dinitrogen sulfide
• D. nitrogen sulfide
• E. nitrogen sulfite

Here’s what students ask on this topic:

What are binary molecular compounds and how are they named?

Binary molecular compounds consist of two different nonmetals, such as water (H₂O) and nitrogen oxides (NO). Naming these compounds involves using numerical prefixes to indicate the number of atoms of each element. The first nonmetal retains its name without the prefix 'mono,' while the second nonmetal adopts the 'ide' suffix. For example, CO is carbon monoxide, and CO₂ is carbon dioxide. If a prefix ending in 'a' precedes 'o', the 'a' is dropped, as in 'tetroxide' for four oxygens. Understanding these rules is essential for accurate chemical communication.

What are the numerical prefixes used in naming binary molecular compounds?

The numerical prefixes used in naming binary molecular compounds are: mono (1), di (2), tri (3), tetra (4), penta (5), hexa (6), hepta (7), octa (8), nona (9), and deca (10). These prefixes indicate the number of atoms of each element in the compound. For example, N₂O₄ is named dinitrogen tetroxide, where 'di' indicates two nitrogen atoms and 'tetra' indicates four oxygen atoms.

Why is the prefix 'mono' not used for the first nonmetal in binary molecular compounds?

The prefix 'mono' is not used for the first nonmetal in binary molecular compounds to avoid redundancy and simplify naming. For example, CO is named carbon monoxide, not monocarbon monoxide. This convention helps streamline the naming process and makes the names easier to pronounce and remember.

How do you name a binary molecular compound with the formula P₂O₅?

To name the binary molecular compound P₂O₅, follow these steps: First, name the first nonmetal (phosphorus) and use the appropriate numerical prefix (di) to indicate two atoms, resulting in 'diphosphorus.' Next, name the second nonmetal (oxygen) with the 'ide' suffix and the appropriate numerical prefix (penta) to indicate five atoms, resulting in 'pentoxide.' Therefore, P₂O₅ is named diphosphorus pentoxide.

What is the rule for dropping the letter 'a' in numerical prefixes when naming binary molecular compounds?

When naming binary molecular compounds, if a numerical prefix ending in 'a' is followed by a nonmetal name starting with 'o,' the 'a' is dropped to avoid awkward pronunciation. For example, 'tetraoxide' becomes 'tetroxide.' This rule helps make the names of compounds easier to say and more fluid.