FC Writing Chemical Formulas Review - Vocabulary Flashcards

Identify compound type first: ionic (metal + nonmetal or polyatomic ion) vs covalent (nonmetals) vs acids (special cases with H and oxyanions).
For binary ionic compounds: balance charges to get the formula (cation charge + anion charge = 0).
For binary covalent compounds: use prefixes to indicate subscripts (mono-, di-, tri-, etc.), with the second element usually ending in -ide when applicable.
For acids: distinguish binary acids (hydro- prefix, e.g., HF) from oxyacids (polyatomic anions with -ate or -ite; names shift to -ic or -ous and add H in the formula).
When in doubt, verify oxidation states and typical nomenclature patterns for phosphorus, manganese, chromium, tin, etc.
Always express formulas with proper subscripts in LaTeX form: $ext{A}x ext{B}y$ . Use double-dollar delimiters for any chemical expression.
Practical note: precise formulas are essential for stoichiometry, safety, and reproducibility in lab work.

Name: diboron trisulfide
Type: binary covalent (molecular) compound
Formula: $ext{B}2 ext{S}3$
Rationale: use prefixes di- and tri- for B and S, respectively; nonmetals form covalent bonds.
Additional note: common error is to confuse subscripts; ensure the lowest whole-number ratio.

Name: lead(II) oxide
Type: ionic compound (binary salt)
Formula: $ext{PbO}$
Rationale: lead in +2 oxidation state; oxide is O$^{2-}$; charges balance as 1:1.

Note on naming: the term “hydrophosphoric acid” is not standard. In phosphorus oxyacid nomenclature, common relevant acids are phosphoric (H$3$PO$4$), phosphorous (H$3$PO$3$), and hypophosphorous (H$3$PO$2$).
Most likely intended as hypophosphorous acid; formula: $ext{H}3 ext{PO}2$
If instead the intent was another phosphorus oxyacid, the corresponding formulas would be H$3$PO$3$ (phosphorous acid) or H$3$PO$4$ (phosphoric acid).

Name: tin(IV) hydroxide
Type: ionic/hydroxide-containing compound
Formula: $ext{Sn(OH)}_4$
Rationale: tin in +4 oxidation state; hydroxide is OH$^-$; balance with four OH groups.

Name: sodium oxide
Type: ionic compound
Formula: $ext{Na}_2 ext{O}$
Rationale: Na$^+$ (group 1) combines with O$^{2-}$; 2 Na$^+$ per O$^{2-}$ for charge balance.

Name: perbromic acid
Type: oxyacid
Formula: $ext{HBrO}_4$
Rationale: derivative of bromate BrO$3^-$ with one additional H; oxidation state considerations lead to HBrO$4$.

Name: phosphorus pentabromide
Type: covalent compound
Formula: $ext{PBr}_5$
Rationale: phosphorus forms a covalent compound with bromine; no ionic charges involved.

Name: fluorous acid
Note on naming: the standard term is hydrofluoric acid for HF (binary acid).
Formula: $ext{HF}$
Rationale: binary acid formed from hydrogen and a halogen; common lab acid with fluorine.

Name: chromium(II) nitride
Type: ionic nitride compound
Formula: $ext{Cr}3 ext{N}2$
Rationale: chromium(II) provides Cr$^{2+}$; nitride is N$^{3-}$; combine in the ratio that balances charges: 3 Cr$^{2+}$ (total +6) with 2 N$^{3-}$ (total −6).

Name: magnesium nitride
Type: ionic nitride
Formula: $ext{Mg}3 ext{N}2$
Rationale: Mg$^{2+}$; N$^{3-}$; 3 Mg$^{2+}$ (total +6) balances 2 N$^{3-}$ (total −6).

Name: permanganic acid
Type: oxyacid
Formula: $ext{HMnO}_4$
Rationale: permanganate-derived acid; one hydrogen attached to the MnO$4^-$ unit leads to HMnO$4$.

Binary ionic compounds: combine a metal cation with a nonmetal anion or polyatomic ion (e.g., CaSO$3$, Na$2$O, Ba(OH)$_2$).
Binary covalent compounds: use prefixes to denote subscripts (e.g., B$2$S$3$, PBr$_5$). For silicon tetrachloride, the subscript 4 comes from the chlorine ligands, not a prefix.
Oxyacids: hydrogen combines with oxyanions; -ate vs -ite endings influence the acid name (-ic acid vs -ous acid in many cases). For example, HBrO$4$ (perbromic acid) vs HBrO$2$ (bromous acid) would follow this logic.
Hydro-binary acids: hydro- prefix indicates binary acids like HF (hydrofluoric acid).

These practice problems reinforce the core rule: balance charges for ionic compounds, apply prefixes for covalent compounds, and apply acid nomenclature for oxyacids.
Accurate formulas are essential for stoichiometry calculations, yield predictions, and safety data in real-world labs.
Misnaming items (as seen with the ambiguous item 4) highlights the importance of standardized nomenclature and cross-checking against common chemical families.