Worksheet on naming molecular compounds, featuring a table of chemical formulas and their names, along with related questions for students.

You're looking at a worksheet titled “Naming Molecular Compounds”, which teaches how to name covalent (molecular) compounds using prefixes based on the number of atoms.

Let’s go through each question and explain the answers clearly:

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Question 1: Fill in the table to indicate the number of atoms of each type in the molecular formula.

The table already has some numbers filled in — let’s verify and complete it:

| Molecular Formula | Number of Atoms of First | Number of Atoms of Second | Name of Compound |
|-------------------|--------------------------|---------------------------|------------------------------|
| ClF | 1 | 1 | Chlorine monofluoride |
| ClF₅ | 1 | 5 | Chlorine pentafluoride |
| CO | 1 | 1 | Carbon monoxide |
| CO₂ | 1 | 2 | Carbon dioxide |
| Cl₂O | 2 | 1 | Dichlorine monoxide |
| PCl₅ | 1 | 5 | Phosphorus pentachloride |
| N₂O₅ | 2 | 5 | Dinitrogen pentoxide |

✔ All entries are correct as shown in your image.

> *Note: “First” refers to the first element in the formula, “Second” refers to the second element.*

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Question 2: Examine the molecular formulas...

#### a. How many different elements are present in each compound shown?

✔ Answer: Two

All compounds listed contain exactly two different elements — for example:
- ClF → chlorine + fluorine
- CO → carbon + oxygen
- PCl₅ → phosphorus + chlorine

This is typical for binary molecular compounds.

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#### b. Do the compounds combine metals with metals, metals with nonmetals, or nonmetals with nonmetals?

✔ Answer: Non-metals with non-metals

Look at the elements:
- Chlorine (Cl), Fluorine (F), Oxygen (O), Carbon (C), Phosphorus (P), Nitrogen (N) — all are nonmetals.

Molecular compounds form between nonmetal + nonmetal via sharing electrons (covalent bonding).

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#### c. Based on your answer to b, what type of bonding must be involved in molecular compounds?

✔ Answer: Covalent bonds

Since nonmetals share electrons to achieve stable electron configurations, they form covalent bonds. This is why these are called *molecular* compounds — they exist as discrete molecules held together by covalent bonds.

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Question 3: Find all the compounds in Model 1 that have chlorine and fluorine in them. Explain why the name “chlorine fluoride” is not sufficient to identify a specific compound, but does not reflect the difference.

✔ Compounds with chlorine and fluorine:
- ClF → chlorine monofluoride
- ClF₅ → chlorine pentafluoride

✔ Why “chlorine fluoride” is not sufficient:

Both compounds contain chlorine and fluorine, but they have different numbers of fluorine atoms:
- ClF has 1 fluorine atom
- ClF₅ has 5 fluorine atoms

If you just say “chlorine fluoride”, people won’t know which one you mean. That’s why we use prefixes like *mono-*, *penta-* to specify the exact number of atoms.

> 🔍 Key Point: The prefix tells us the number of atoms of each element. Without it, the name is ambiguous.

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Question 4: Assuming that the name of the compound gives a clue to its molecular formula, predict how many atoms each of these prefixes indicates, and provide two examples.

This question asks you to interpret the Greek prefixes used in naming molecular compounds.

Here’s the standard prefix system:

| Prefix | Number of Atoms |
|----------|------------------|
| mono- | 1 |
| di- | 2 |
| tri- | 3 |
| tetra- | 4 |
| penta- | 5 |
| hexa- | 6 |
| hepta- | 7 |
| octa- | 8 |
| nona- | 9 |
| deca- | 10 |

✔ Examples from the table:

1. Dichlorine monoxide (Cl₂O)
- *Di-* = 2 chlorine atoms
- *Mono-* = 1 oxygen atom

2. Dinitrogen pentoxide (N₂O₅)
- *Di-* = 2 nitrogen atoms
- *Penta-* = 5 oxygen atoms

✔ Another example (not in table):
- Carbon tetrachloride (CCl₄) → *tetra-* = 4 chlorine atoms

> 📝 Note: The prefix *mono-* is often omitted for the first element (e.g., CO is “carbon monoxide”, not “monocarbon monoxide”), but it’s always used for the second element if there’s only one atom.

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## ✔ Final Summary:

- Molecular compounds are made of two nonmetals bonded covalently.
- Names use Greek prefixes to show the number of atoms of each element.
- Prefixes like *di-*, *tri-*, *penta-* tell us exactly how many atoms are present.
- Without prefixes, names would be ambiguous — e.g., “chlorine fluoride” could mean ClF or ClF₅.

This system ensures precise communication in chemistry — critical when small differences (like CO vs. CO₂) can mean life or death!

Let me know if you’d like to practice naming more compounds! 😊