Atomic structure & nomenclature (Chapter 2)

Nomenclature overview: naming rules differentiate ionic vs molecular compounds and acids.

• Be able to name:

  • Constituent atoms in molecular compounds

  • Constituent ions in ionic compounds

  • Ionic compounds

  • Molecular compounds

  • Acids

Naming ionic compounds: cation name followed by anion name.

• Examples: name the following ionic compounds: CaBr₂, Mg(OH)₂, Co₂O₃, TiCl₂, (NH₄)₂CO₃, Na₂SO₄, NaHSO₄.

• Predict charges on simple cations and anions where possible.

Naming monatomic cations: (group 1A, 2A, 3A, and some d-block metals) the name is simply the metal name followed by “ion.”

Continuation: same rule for monatomic cations with single oxidation state.

Transition metals with multiple oxidation states:

• New method: write the charge in parentheses after the metal name and before “ion.”

• Old method (historical): use latin root with “ous” for lower charge, and “ic” for higher charge, followed by “ion.”

Polyatomic cations: common ones include ammonium (NH₄⁺).

• Polyatomic cations include NH₄⁺; other polyatomic ions are listed in tables.

Naming monatomic anions: drop the ending of the element name and add “-ide” + “ion.”

• Examples: H⁻, N³⁻, O²⁻, F⁻, S²⁻, Br⁻.

Polyatomic anions (continued): many common polyatomic anions and their charges.

Naming polyatomic anions: some end in -ide (e.g., hydroxide, cyanide, peroxide, azide).

• Hydrogens can form hydrogen oxyanions when combined with oxyanions (e.g., HXO_n^m⁻).

Oxyanions are very common. Typical rules:

• Elements that form only two oxyanions have the same charges on both (one with fewer oxygens is the “ite” form; more oxygens is the “ate”).

• Elements that form three or four oxyanions also follow similar patterns; hypo = fewer oxygens; per = more oxygens.

• Hydrogen ions (H⁺) can combine with oxyanions to form hydrogen oxyanions (e.g., HNO₂, HNO₃).

Memorization tip for common oxyanions (XOnm⁻): carbonate, nitrate, phosphate, sulfate, perchlorate, ammonium, etc. Some formulas and names to remember for exam use.

More on polyatomic ion naming rules and example formulas: reiterates common ions and the need to memorize some hydroxide and related species.

Additional notes on oxyanions naming and examples for nitrogen, sulfur, and phosphorus oxyanions (NO₂⁻, NO₃⁻; SO₃²⁻, SO₄²⁻; PO₃³⁻, PO₄³⁻).

Recap on oxyanion naming rules with examples for chlorate, chlorite, hypochlorite, perchlorate, etc.; confirms consistency of “ite” vs “ate” and hypo/per for halogen oxyanions.

More on carbonate, sulfate, nitrate, phosphate, and related oxyanions; reaffirmation of common ions and formulas.

Oxyanions continued: additional examples (thiosulfate S₂O₃²⁻, dithionate S₂O₆²⁻, tetrathionate S₄O₆²⁻).

Oxyanions formed with metals (e.g., MnO₄⁻ = permanganate, Cr₂O₇²⁻ = dichromate): notes that these are common but not required to memorize all names now.

Summary of oxyanion patterns and special cases; the focus is on understanding patterns rather than memorizing every exotic ion.

Oxyanions and hydrogen-containing variants: hydrogen oxyanions HXO_n form when H⁺ is added to oxyanions; common patterns noted.

Exam information on essential polyatomic ion formulas and the hydroxide ion OH⁻ needs to be known.

Nomenclature recap: Ionic vs covalent (molecular) compounds; acids included in naming conventions.

Naming ionic compounds (summary): cation name first, followed by anion name; practical examples given above.

Acids: simple working definition — a compound that dissolves in water to produce hydrogen ions (H⁺) and a corresponding anion X⁻ or Xⁿ⁻.

Binary acids naming rules:

• Start with “hydro”

• Replace the “-ide” suffix of the anion with “-ic”

• Add the word “acid” (e.g., HCl → hydrochloric acid).

Acids formed from oxyanions:

• If the oxyanion ends with “ite,” the acid name ends with “-ous acid.”

• If the oxyanion ends with “ate,” the acid name ends with “-ic acid.”

• Retain “hypo” or “per” if present in the oxyanion name.

• Example: NO₂⁻ becomes nitrous acid (HNO₂); NO₃⁻ becomes nitric acid (HNO₃).

• General form: H⁺ + XOnm⁻ → HxOnm (an acid).

Oxyanion to oxyacid mapping (examples):

• NO₂⁻ → nitrous acid, HNO₂

• NO₃⁻ → nitric acid, HNO₃

• ClO⁻ → hypochlorous acid, HClO

• ClO₂⁻ → chlorous acid, HClO₂

• ClO₃⁻ → chloric acid, HClO₃

• ClO₄⁻ → perchloric acid, HClO₄

• CO₃²⁻ → carbonic acid, H₂CO₃

• SO₃²⁻ → sulfurous acid, H₂SO₃

• SO₄²⁻ → sulfuric acid, H₂SO₄

• PO₃³⁻ → phosphorous acid, H₃PO₃

• PO₄³⁻ → phosphoric acid, H₃PO₄

Naming molecular compounds (nonmetals only; often binary):

• The element closer to the metals is listed first.

• The first element is named with its normal name.

• The second element is named with its suffix changed to “-ide.”

• Use prefixes to indicate the number of atoms in the compound (do not use the prefix “mono” for the first element).

Prefixes used for binary molecular compounds:

• mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca

Naming rules reminder (binary molecular compounds):

• Element closer to metals listed first; first element uses its standard name; second element ends with -ide; prefixes denote the number of atoms.

Naming tips wrap-up: ensure correct prefixes and endings to yield unambiguous names for binary molecular compounds.

A light, humorous slide about a bar joke illustrating atomic naming concepts (H₂O → life or death joke).

Practice: Name these molecular and ionic compounds (examples include NF₃, C₆H₁₄, K₂S, P₄S₃, MgO, KBr, OF₂, AsH₃, XeF₂, NaF, PbF₂, P₂F₄).

Answer key examples (partial):

• NF₃: molecular (nitrogen trifluoride) — empirical likely not applicable (molecular mass indicates molecular formula equals empirical in many simple cases).

• MgO: ionic (magnesium oxide).

• XeF₂: molecular (xenon difluoride).

• NaF: ionic (sodium fluoride).

• PbF₂: ionic (lead(II) fluoride).

• P₂F₄: molecular (diphosphorus tetrafluoride).

• etc. (practice problems consolidate understanding of ionic vs molecular and empirical vs molecular formulas).

Practice: Write formulas for ionic compounds given names (e.g., ammonium nitrate, cobalt(II) nitrate, nickel(II) sulfate, nickel(III) cyanide, vanadium(III) oxide, ammonium sulfate).

• Reminder: Polyatomic ions (CO₃²⁻, NO₃⁻, SO₄²⁻, PO₄³⁻, NH₄⁺, ClO₃⁻, etc.) are used in many ionic formulas.

Additional practice: Write formulas for the same set of ionic compounds; emphasize balancing charges and recognizing polyatomic ions.

Name the following molecular and ionic compounds:

• MgBr₂, Li₂CO₃, KHSO₃, KMnO₄, (NH₄)₂S, CuCl, CuCl₂

Give formulas for: a) Carbon dioxide, b) Phosphorus triiodide, c) Sulfur dichloride, d) Xenon trioxide, e) Dioxygen difluoride

Name the following molecular compounds: a) N₂F₄, b) HBr, c) SF₄, d) ClF₃, e) BCl₃, f) P₄O₁₀

Learning objectives for Chapter 2 (summary):

• Explain atomic theory and atom composition; define isotope; represent atoms using symbols with superscripts/subscripts denoting composition.

• Use the Periodic Table to rationalize similarities/differences among elements; predict common ion charges based on group position (1A, 2A, 3A, 5A, 6A, 7A).

• Name and predict ions formed from elements; recognize common polyatomic ions and ions in acids.

• Differentiate ionic vs molecular compounds and empirical vs molecular formulas.

• Given a chemical formula, provide a proper systematic name; conversely, deduce the formula from a name.

• Properly name binary acids and acids formed from oxyanions.

1. Covalent Compounds (nonmetal + nonmetal)

Use prefixes to show the number of atoms.

⚡ Rules:

• Drop the “o” or “a” if the next element starts with a vowel (e.g., pentaoxide → pentoxide).

• First element does not use “mono-”.

2. Ionic Compounds (metal + nonmetal/polyatomic ion)

• No prefixes.

• Metal (cation) named first, nonmetal/polyatomic (anion) second.

• Transition metals may use Roman numerals for charge.

Examples:

• NaCl = sodium chloride

• FeCl₂ = iron(II) chloride

• FeCl₃ = iron(III) chloride

• Zn₃(PO₄)₂ = zinc phosphate

3. Polyatomic Ions with Oxygen (oxyanions)

4. Older Cation Naming (-ous vs -ic)

Used for metals with variable charges (less common now, replaced by Roman numerals).

5. Acids

(a) Binary acids (H + nonmetal, no O)

• hydro-…-ic acid

• Example:

  • HCl = hydrochloric acid

  • HBr = hydrobromic acid

(b) Oxyacids (H + polyatomic ion with O)

• -ate → -ic acid

• -ite → -ous acid

• per-…-ate → per-…-ic acid

• hypo-…-ite → hypo-…-ous acid

Examples:

• HNO₃ (nitrate, NO₃⁻) → nitric acid

• HNO₂ (nitrite, NO₂⁻) → nitrous acid

• HClO₄ (perchlorate, ClO₄⁻) → perchloric acid

• HClO (hypochlorite, ClO⁻) → hypochlorous acid

6. Quick Master Pattern

• Prefixes (mono-, di-, tri-, etc.) = covalent compounds

• -ide = simple anion or binary acid (hydro-…-ic acid)

• -ate → -ic acid

• -ite → -ous acid

• per-/hypo- = highest/lowest oxygen in oxyacids

• -ous vs -ic = lower/higher cation charges (older system)

⚡ So if you see:

• oxide, chloride, sulfide → simple anion → “hydro-…-ic acid” when with H.

• nitrate, sulfate, phosphate → “-ate” → becomes “-ic acid” when with H.

• nitrite, sulfite, chlorite → “-ite” → becomes “-ous acid” when with H.

• per-…-ate / hypo-…-ite → carry prefixes into acid names.