Question

identify the formula units for each particle. not all units will be used, some will be used more than once
co₂
fe₂o₃
li
br₂
moles molecules formula units atoms

Explanation:

Step1: Analyze \( \text{CO}_2 \)

\( \text{CO}_2 \) is a covalent compound (molecular compound). The particle units for molecular compounds can be molecules (when referring to individual discrete units) or moles (amount), but for the formula unit type, for molecular compounds, the formula unit is also the molecular formula, and we can refer to their particles as molecules (or moles, but in terms of the particle type here, \( \text{CO}_2 \) particles are molecules (or can be in moles, but let's match the options). Wait, actually, for \( \text{CO}_2 \):
- Moles: can be used (amount), but the particle type (the formula unit's particle) for molecular compounds: \( \text{CO}_2 \) particles are molecules. But also, moles can be applied to any substance. Wait, maybe better to recall:
- Atoms: for single atoms (like Li).
- Molecules: for covalent/molecular compounds (like \( \text{CO}_2 \), \( \text{Br}_2 \)).
- Formula units: for ionic compounds (like \( \text{Fe}_2\text{O}_3 \)).
- Moles: is an amount unit, can be used for any substance (but the question is about the formula units for each particle, so maybe the particle type). Wait, the question says "Identify the formula units for each particle". Wait, maybe rephrasing: what is the particle type (in terms of the options: moles, molecules, formula units, atoms) for each substance.

So:
- \( \text{CO}_2 \): molecular compound, so its particles are molecules (or formula unit is the molecular formula, but the particle type here would be molecules (or moles, but moles is amount). Wait, the options are moles, molecules, formula units, atoms.

Let's clarify each substance:

1. \( \text{CO}_2 \): covalent (molecular) compound. The basic particle is a molecule. Also, we can have moles of \( \text{CO}_2 \), but the particle type (the formula unit's particle) – for molecular compounds, the formula unit is the molecule. So \( \text{CO}_2 \) particles can be molecules (or moles, but moles is amount). Wait, maybe the question is about what type of particle (atom, molecule, formula unit) or the unit (moles is amount, but the other options are particle types). Wait, maybe the options are the types of particles or the units to describe the amount? Wait, the options are: moles (amount), molecules (particle), formula units (particle for ionic), atoms (particle).

So:

- \( \text{Li} \): is an element, a metal, exists as atoms (or in metallic lattice, but the particle type is atoms). So \( \text{Li} \) particles are atoms.

- \( \text{Fe}_2\text{O}_3 \): ionic compound (iron(III) oxide), so its formula unit is \( \text{Fe}_2\text{O}_3 \), and the particle type is formula units (since ionic compounds are made of ions, but the formula unit is the simplest ratio, and we refer to their particles as formula units).

- \( \text{Br}_2 \): diatomic molecular element, so its particles are molecules (or atoms? No, \( \text{Br}_2 \) is a molecule made of two Br atoms). So \( \text{Br}_2 \) particles are molecules.

- \( \text{CO}_2 \): molecular compound, particles are molecules.

- \( \text{Fe}_2\text{O}_3 \): ionic, particles are formula units.

- \( \text{Li} \): particle is atom.

- \( \text{Br}_2 \): particle is molecule.

Also, moles is an amount unit, so any substance can be in moles, but the question is about the formula units (the particle type) for each particle. Wait, maybe the question is matching each substance to the appropriate particle type (atoms, molecules, formula units) or moles (but moles is amount). Let's proceed:

- \( \text{CO}_2 \): molecules (or moles, but moles is amount. Wait, the options include moles. Maybe the question is about the unit (moles) or the particle type. Let's check each:

1. \( \text{CO}_2 \):
- Moles: can be used (amount of \( \text{CO}_2 \) is in moles), but also, the particle is a molecule. But the options are moles, molecules, formula units, atoms. Let's see the standard:

- Atoms: for single atoms (Li).

- Molecules: for molecular compounds (CO₂, Br₂).

- Formula units: for ionic compounds (Fe₂O₃).

- Moles: is an amount unit, so any substance can be measured in moles, but the question is about the formula units for each particle, so maybe the particle type (atom, molecule, formula unit) or the unit (moles). Wait, maybe the question is a bit ambiguous, but let's match:

- \( \text{CO}_2 \): molecules (or moles, but moles is amount. Wait, maybe the answer is:

- \( \text{CO}_2 \): molecules (or moles, but let's check the other substances.

- \( \text{Fe}_2\text{O}_3 \): formula units (ionic compound).

- \( \text{Li} \): atoms.

- \( \text{Br}_2 \): molecules.

Also, moles can be applied to all, but maybe the question is about the particle type (atom, molecule, formula unit) and moles is an amount. Let's confirm:

- Ionic compounds (like \( \text{Fe}_2\text{O}_3 \)): their formula units are the ionic formula, and the particles are formula units (since they form a lattice, not discrete molecules).

- Molecular compounds (like \( \text{CO}_2 \), \( \text{Br}_2 \)): their particles are molecules.

- Elemental metals (like Li) or noble gases: particles are atoms.

So:

- \( \text{CO}_2 \): molecules (or moles, but moles is amount. Wait, the options include moles. Maybe the question is about the unit (moles) as the formula unit? No, formula unit is the chemical formula. Wait, maybe the question is to match each substance to the appropriate unit (moles) or particle type (molecules, formula units, atoms). Let's proceed with the standard matching:

- \( \text{CO}_2 \): molecules (or moles, but let's see the options. If we have to choose from the four: moles, molecules, formula units, atoms.

Let's list each:

1. \( \text{CO}_2 \):
- Molecules: yes, as it's a molecular compound.
- Moles: yes, as an amount. But which is correct? Wait, the question says "formula units for each particle". Maybe the formula unit is the chemical formula, and the particle type (the unit of the particle) – for \( \text{CO}_2 \), the particle is a molecule, so the formula unit's particle is a molecule. So \( \text{CO}_2 \) → molecules (or moles, but moles is amount).

2. \( \text{Fe}_2\text{O}_3 \): ionic compound, so formula unit is \( \text{Fe}_2\text{O}_3 \), and the particle is a formula unit (since it's ionic, no discrete molecules). So \( \text{Fe}_2\text{O}_3 \) → formula units.

3. \( \text{Li} \): elemental metal, particle is an atom. So \( \text{Li} \) → atoms.

4. \( \text{Br}_2 \): diatomic molecule, particle is a molecule. So \( \text{Br}_2 \) → molecules.

Also, moles can be used for any substance, but maybe the question is about the particle type (atom, molecule, formula unit) and moles is an amount unit. But the options include moles. Wait, maybe the question is that "moles" is an amount unit that can be applied to any substance, but the other options are particle types. Let's check:

- \( \text{CO}_2 \): can be in moles (amount) and its particles are molecules. But the question is to identify the formula units (the particle type) for each particle. Maybe the intended matches are:

- \( \text{CO}_2 \): molecules (or moles, but let's see the standard problem like this: usually,

- Atoms: Li

- Molecules: CO₂, Br₂

- Formula units: Fe₂O₃

- Moles: can be any, but maybe the question has moles as an option, but perhaps the intended is:

Let's do the matching:

- \( \text{CO}_2 \): molecules (or moles, but let's check the options. The options are moles, molecules, formula units, atoms.

Let's list each:

1. \( \text{CO}_2 \):
- Molecules: yes (particle is molecule)
- Moles: yes (amount)
But which is correct? Wait, maybe the question is about the "formula unit" as the chemical formula, and the particle type (the unit of the formula unit). For molecular compounds, the formula unit is the molecular formula, and the particle is a molecule. So \( \text{CO}_2 \) → molecules.

2. \( \text{Fe}_2\text{O}_3 \): ionic compound, formula unit is \( \text{Fe}_2\text{O}_3 \), particle is formula unit → formula units.

3. \( \text{Li} \): particle is atom → atoms.

4. \( \text{Br}_2 \): particle is molecule → molecules.

Also, moles can be used for any, but maybe the question is that moles is an amount unit that can be applied to all, but the other options are particle types. But the problem says "Not all units will be used, some will be used more than once". So:

- \( \text{CO}_2 \): molecules (or moles, but let's go with molecules)

- \( \text{Fe}_2\text{O}_3 \): formula units

- \( \text{Li} \): atoms

- \( \text{Br}_2 \): molecules

And moles can be used for any, but maybe the question has moles as an option, but perhaps the intended is:

So the matching is:

- \( \text{CO}_2 \) → molecules

- \( \text{Fe}_2\text{O}_3 \) → formula units

- \( \text{Li} \) → atoms

- \( \text{Br}_2 \) → molecules

And moles is an option that can be used for any, but maybe the question has moles as a distractor, but in typical problems, this is the matching.

Step2: Analyze \( \text{Fe}_2\text{O}_3 \)

\( \text{Fe}_2\text{O}_3 \) is an ionic compound (iron(III) oxide). Ionic compounds do not exist as discrete molecules but as a lattice of ions. The formula unit (the simplest ratio of ions in the lattice) is \( \text{Fe}_2\text{O}_3 \), so the particle type for \( \text{Fe}_2\text{O}_3 \) is formula units.

Step3: Analyze \( \text{Li} \)

\( \text{Li} \) is a metallic element. The basic particle of a metal is an atom (in the metallic lattice, we can consider the particles as atoms), so the particle type for \( \text{Li} \) is atoms.

Step4: Analyze \( \text{Br}_2 \)

\( \text{Br}_2 \) is a diatomic molecular element (bromine exists as \( \text{Br}_2 \) molecules). So the particle type for \( \text{Br}_2 \) is molecules.

Also, note that "moles" is a unit of amount (amount of substance) and can be applied to any of these substances (e.g., moles of \( \text{CO}_2 \), moles of \( \text{Fe}_2\text{O}_3 \), moles of \( \text{Li} \), moles of \( \text{Br}_2 \)), but the question is about the formula units (the particle type) for each particle, so we match the particle type (atoms, molecules, formula units) and moles is an amount unit. But since the options include moles, maybe the intended is:

- \( \text{CO}_2 \): molecules (or moles, but let's go with the particle type)

- \( \text{Fe}_2\text{O}_3 \): formula units

- \( \text{Li} \): atoms

- \( \text{Br}_2 \): molecules

And moles can be used for any, but in the problem's context, this is the matching.

Answer:

• \( \text{CO}_2 \): molecules (or moles, but based on particle type, molecules)
• \( \text{Fe}_2\text{O}_3 \): formula units
• \( \text{Li} \): atoms
• \( \text{Br}_2 \): molecules

(If we consider moles as an amount unit applicable to all, but the typical matching for this type of problem is as above, with \( \text{Li} \) → atoms, \( \text{Fe}_2\text{O}_3 \) → formula units, \( \text{CO}_2 \) and \( \text{Br}_2 \) → molecules.)

To present the final matches (assuming the question is to connect each substance to the correct particle type/unit):

• \( \text{CO}_2 \) → molecules
• \( \text{Fe}_2\text{O}_3 \) → formula units
• \( \text{Li} \) → atoms
• \( \text{Br}_2 \) → molecules

(Note: "moles" is an amount unit that can apply to all, but the other options are particle types, and this is the standard matching for such problems.)