Chemical Nomenclature and Formulas Flashcards

Chemical Formulas and Compound Types

• Chemical Nomenclature: Systematic approach used to name chemical compounds.

• Chemical Formulas: Representation of compounds combining elemental symbols and numerical subscripts.

  • Subscripts indicate the number of atoms of each element in a formula unit.

  • Parentheses group multiple polyatomic units together (e.g., $1$ formula unit of $\text{Ba}_3(\text{PO}_4)_2$ contains $3$ $\text{Ba}$ atoms, $2$ $\text{P}$ atoms, and $8$ $\text{O}$ atoms; $1$ formula unit of $(\text{NH}_4)_2\text{SO}_3$ contains $2$ $\text{N}$ atoms, $8$ $\text{H}$ atoms, $1$ $\text{S}$ atom, and $3$ $\text{O}$ atoms).

• Allotropes: Distinct molecular forms of the same element.

  • Oxygen allotropes: Molecular oxygen ($\text{O}_2$) and ozone ($\text{O}_3$).

  • Carbon allotropes: Diamond (hard, colorless), graphite (soft, gray), nanotubes, and fullerenes.

• Compound Classification:

  • Covalent Compounds: Composed of nonmetal atoms bonded together via covalent bonds; represented as individual particles called molecules.

  • Ionic Compounds: Composed of metal (cation) and nonmetal (anion) atoms; arranged in an extended 3-D lattice structure representing a fixed ratio of atoms.

Naming Binary Ionic Compounds

• General Rule: The cation (metal) is always named first, followed by the anion (nonmetal).

• Type I Ionic Compounds (Fixed-Charge Metals):

  • Metal forms only one charge state.

  • Name = Cation Element Name + Anion Root + -ide.

  • Examples: $\text{AlCl}_3$ is aluminum chloride; $\text{SrBr}_2$ is strontium bromide.

• Type II Ionic Compounds (Variable-Charge Metals):

  • Metal (typically transition metals) forms two or more cations with different charges.

  • Charge state is indicated by a Roman numeral in parentheses.

  • Name = Cation Element Name + (Roman Numeral) + Anion Root + -ide.

  • Examples: $\text{Fe}_2\text{O}_3$ is iron(III) oxide ($\text{Fe}^{3+}$ and $\text{O}^{2-}$); $\text{FeBr}_3$ is iron(III) bromide; $\text{FeBr}_2$ is iron(II) bromide; $\text{CuBr}$ is copper(I) bromide; $\text{PbO}_2$ is lead(IV) oxide.

  • Special cation case: Mercury(I) ions always occur bound together in pairs as $\text{Hg}_2^{2+}$.

Polyatomic Ions and Ionic Nomenclature

• Polyatomic Cations: The primary common polyatomic cation is ammonium ($\text{NH}_4^+$).

• Polyatomic Anions:

  • Most polyatomic anions contain oxygen (oxyanions).

  • Hydroxide ($\text{OH}^-$) and cyanide ($\text{CN}^-$) are the only polyatomic anions ending in -ide.

• Oxyanion Naming Series:

  • per- + root + -ate (maximum oxygen atoms, e.g., $\text{ClO}_4^-$ perchlorate)

  • root + -ate (base oxygen count, e.g., $\text{ClO}_3^-$ chlorate)

  • root + -ite (one fewer oxygen atom, e.g., $\text{ClO}_2^-$ chlorite)

  • hypo- + root + -ite (two fewer oxygen atoms, e.g., $\text{ClO}^-$ hypochlorite)

• Polyatomic Ionic Examples:

  • $\text{NaOH}$: Sodium hydroxide

  • $\text{Mg}(\text{NO}_3)_2$: Magnesium nitrate

  • $(\text{NH}_4)_2\text{SO}_4$: Ammonium sulfate

  • $\text{FePO}_4$: Iron(III) phosphate

Naming Binary Covalent Compounds (Type III)

• Composition: Formed between two nonmetals.

• Naming Steps:

  1. First nonmetal: Use the full element name with a Greek numerical prefix indicating quantity (omit mono- for the first element).

  2. Second nonmetal: Named like an anion using its root + -ide, preceded by a Greek numerical prefix.

• Greek Prefixes:

  • $1$: mono-

  • $2$: di-

  • $3$: tri-

  • $4$: tetra-

  • $5$: penta-

  • $6$: hexa-

  • $7$: hepta-

  • $8$: octa-

  • $9$: nona-

  • $10$: deca-

• Examples:

  • $\text{N}_2\text{O}$: Dinitrogen monoxide

  • $\text{N}_2\text{O}_4$: Dinitrogen tetroxide

  • $\text{SeO}_2$: Selenium dioxide

  • $\text{OF}_2$: Oxygen difluoride

  • $\text{SO}_2$: Sulfur dioxide

Acid Nomenclature

• Acid Definition: Molecules containing one or more $\text{H}^+$ ions attached to an anion, recognized by hydrogen written first in the formula (e.g., $\text{HCl}$).

• Acids Without Oxygen:

  • Prefix hydro- + Anion Root + -ic acid.

  • Examples:

  • $\text{HF}$: Hydrofluoric acid

  • $\text{HCl}$: Hydrochloric acid

  • $\text{HBr}$: Hydrobromic acid

  • $\text{HI}$: Hydroiodic acid

  • $\text{HCN}$: Hydrocyanic acid

  • $\text{H}_2\text{S}$: Hydrosulfuric acid

• Oxygen-Containing Acids (Oxyacids):

  • If the polyatomic anion ends in -ate ——> + -ic acid.

  • $\text{HNO}_3$ ($\text{NO}_3^-$ nitrate): Nitric acid

  • $\text{H}_2\text{SO}_4$ ($\text{SO}_4^{2-}$ sulfate): Sulfuric acid

  • $\text{H}_3\text{PO}_4$ ($\text{PO}_4^{3-}$ phosphate): Phosphoric acid

  • $\text{HC}_2\text{H}_3\text{O}_2$ ($\text{C}_2\text{H}_3\text{O}_2^-$ acetate): Acetic acid

  • If the polyatomic anion ends in -ite ———→+ -ous acid.

  • $\text{HNO}_2$ ($\text{NO}_2^-$ nitrite): Nitrous acid

  • $\text{H}_2\text{SO}_3$ ($\text{SO}_3^{2-}$ sulfite): Sulfurous acid

  • $\text{HClO}_2$ ($\text{ClO}_2^-$ chlorite): Chlorous acid