III. Nomenclature; the Mole, Chemical Bonding and Geometry 14 Questions

● Nomenclature

– Systematic nomenclature of ionic and molecular compounds, including acids

– Nomenclature of organic compounds according to their functional groups

● The mole, chemical bonding, and molecular geometry

– interpret and use chemical formulas

– Mole concept and chemical composition

– Ionic, covalent, and metallic bonding

– Intermolecular forces and correlation to physical properties

– Bond properties and correlation to chemical reactivity

– Structural formulas and molecular geometry

A. Nomenclature

– Systematic nomenclature of ionic and molecular compounds, including acids

– Nomenclature of organic compounds according to their functional groups

Nomenclature, coefficients, subscripts and moles

Valence Shell Electrons

Valence shell electrons are those electrons found in the outer energy level of an atom and are the only electrons capable of bonding. The bonding type depends on the extent to which bonding electrons are shared.  In one extreme electrons are not shared at all but are transferred wholly from the less electronegative to the more electronegative atom.  This is called ionic bonding.  The other extreme sees the electrons equally shared in a bond called a covalent bond.  This occurs in homonuclear diatomic molecules.  In all others, the bonding is somewhere in between the two extremes.

Bonding type may be determined by studying Lewis Structures and electronegativity values, as we'll see later.

The most common number of valence shell electrons "involved in bonding" may be found using this guide. These numbers correspond to oxidation numbers shown on the periodic table or to the number of unpaired valence shell electrons in an element.

The positive sign indicates that if an ion was formed during bonding, electrons would be lost by the element and the resulting ion formed would take on a positive charge.

The negative sign indicates that if an ion was formed during bonding, electrons would be gained by the element and the resulting ion formed would take on a negative charge.

The positive and negative charges would result only if ions are formed. Oxidation numbers give chemists a method of keeping track of electrons.

When you are unsure of an element’s oxidation number, look it up on the periodic table.

Example: What are oxidation numbers of F, Ca, S, Fe?

Summary

• Positively charged ions are called cations
• Negatively charged ions are called anions
• The cation is always named first.
• Cations can be metals or polyatomic ions

• For metals that have only one possible charge (valency) the name of the metal is used.
  Examples are Group I metals (charge 1+), Group II metals (charge 2+), Aluminium (charge 3+), Zinc (charge 2+), Silver (charge 1+)
• For metals that can have more than one charge (valency) the name of the metal is succeeded by the valency in capital Roman numerals in brackets
  OR
  by using the suffix -ous for the lowest valency and -ic for the highest valency and sometimes with the Latinised name for the metal

• The ammonium ion (NH₄⁺) is an example of a polyatomic cation
• Hydrogen can also form a cation, H⁺, in which case the name hydrogen is used in naming.
• Anions can be a negatively charged element or a polyatomic ion
  • Negatively charged elements have the suffix -ide
    Examples are oxide (O^2-), sulfide (S^2-), fluoride (F^-), chloride (Cl^-), bromide (Br^-), iodide (I^-), nitride (N^3-), hydride (H^-)
  • Polyatomic ions which include oxygen in the anion have the suffixes -ate or -ite. "ate" means there is more oxygen in the anion than one ending in "ite"
    Examples: sulfate (SO₄^2-) has more oxygen than sulfite (SO₃^2-), nitrate (NO₃^-) has more oxygen in the anion than nitrite (NO₂^-)
    Other examples are carbonate (CO₃^2-), phosphate (PO₄^3-) and permanganate (MnO₄^-)
    Exception: OH^- is named hydroxide

Examples

• Ionic Compounds containing ions of elements

• MgO
  CATION: Mg²⁺ is named magnesium as magnesium belongs to Group (II) and can only have one charge (valency)
  ANION: O^2- is named oxide
  Name of compound is magnesium oxide
• FeS
  CATION: Fe²⁺ is named iron (II) or ferrous as iron can have a charge of either 2+ or 3+
  ANION: S^2- is named as sulfide
  Name of compound is iron (II) sulfide or ferrous sulfide
• LiH
  CATION: Li⁺ is named as lithium since lithium is a Group I metal and can have only one charge (valency)
  ANION: H^- is named as hydride
  Name of compund is lithium hydride
• H₂S
  CATION: H⁺ is named as hydrogen
  ANION: S^2- is named as sulfide
  Name of compound is hydrogen sulfide
• Ionic compounds containing polyatomic ions
  • NaOH
    CATION: Na⁺ is named as sodium (Group I metal)
    ANION: OH^- is named as hydroxide
    Name of compound is sodium hydroxide
  • CaCO₃
    CATION: Ca²⁺ is named as calcium (Group II metal)
    ANION: CO₃^2- is named as carbonate
    Name of compound is calcium carbonate
  • FeSO₄
    CATION: Fe²⁺ named as iron (II) or ferrous
    ANION: SO₄^2- named as sulfate
    Name of compound is iron (II) sulfate or ferrous sulfate
  • FeSO₃
    CATION: Fe²⁺ named as iron (II) or ferrous
    ANION: SO₃^2- named as sulfite
    Name of compound is iron (II) sulfite or ferrous sulfite
  • (NH₄)₃PO₄
    CATION: NH₄⁺ named as ammonium
    ANION: PO₄^3- named as phosphate
    Name of compound is ammonium phosphate