What is a formula unit? [ENDORSED]

[Audrey Banzali-Marks 1A]

I came across this term in Fundamentals E, and I just wanted to verify that my understanding of the term is correct. Is a formula unit the number of empirical-formula "simplified" molecules that are in one molecule of a substance? For example, if you have one unit of C6H12O6, you actually have 6 formula units of CH2O? Thank you!

[Audrey Banzali-Marks 1A]

Ok, thank you so much! :)

[Ethan Hung 2A]

Is a formula unit the number of empirical-formula "simplified" molecules that are in one molecule of a substance

I believe the term "formula units" is used when referring to ionic compounds as opposed to your typical covalently bonded molecules. Ionic compounds, like NaCl (tablesalt), often form highly regular lattice structures in which there are no chemical bonds. Instead, often large numbers of individual ions are held together by electrostatic attractions (that can be calculated via Coulomb's Law). This means that ionic solids may not be accurately described by a molecular formula, and for this reason, a single unit of an ionic solid may be symbolized using a formula unit instead.

For example, if you have one unit of C6H12O6, you actually have 6 formula units of CH2O?

Not particularly, in this case CH₂O would just be the empirical formula of C₆H₁₂O₆ as opposed to 6 formula units of CH₂O.

Hope that helps :)

[Chem_Mod]

A formula unit is the simplest formula of an ionic compound and therefore you can think of it as the empirical formula of an ionic compound.

But since salts are a repeating solid lattice of ions there is no "molecule" and therefore no "molecular formula" for salts.

Examples of formula units:
NaCl
MgCl₂

I might comment on this in class, but our focus is atoms interacting via covalent bonds to form molecules.

[Chem_Mod]

Please do not post the same question twice.

[305749341]

A formula unit is the simplest form of an ionic compound. While a covalently bonded compound would be referred to as a molecule.