Periodic Table Overview

Classification of Elements

The periodic table organizes elements based on their atomic number and chemical properties. Understanding the classification of elements is essential for predicting their behavior in chemical reactions and their role in compound formation.

• Alkali Metals (Group 1A): Highly reactive metals, form +1 cations.

• Alkaline Earth Metals (Group 2A): Reactive metals, form +2 cations.

• Transition Metals (Groups 3-12 or 1-8B): Metals that often form more than one type of cation.

• Halogens (Group 7A): Nonmetals, highly reactive, typically form -1 anions.

• Noble Gases (Group 8A): Inert gases, very low chemical reactivity.

• Lanthide and Actinide Series: Inner transition metals, often shown separately at the bottom of the table.

Example: Sodium (Na) is an alkali metal and forms Na+ ions in compounds.

Nomenclature Rules for Compounds

Introduction to Compound Types

Chemical compounds are classified into three main types for nomenclature purposes: ionic compounds, binary covalent compounds, and acids. The type of compound determines the rules used for naming.

• Ionic Compounds: Composed of cations (positive ions) and anions (negative ions). Usually formed from metals and nonmetals or polyatomic ions.

• Covalent Compounds: Nonionic, composed only of nonmetals. Atoms share electrons rather than transferring them.

• Acids: Compounds that produce H+ ions in water. Typically have hydrogen written first in the chemical formula.

Naming Ionic Compounds

Identifying Ionic Compounds

To determine if a compound is ionic, check if it contains a metal. Metals lose electrons to form cations, and ionic compounds almost always contain a metal as the cation and a nonmetal as the anion. However, some ionic compounds contain polyatomic cations (e.g., ammonium, NH4+).

• Key Point: If the compound contains a metal, it is most likely ionic.

• Exception: Ionic compounds can also contain polyatomic cations (e.g., NH4+).

Type I and Type II Ionic Compounds

Ionic compounds are further classified based on the type of cation present:

• Type I: Only one possible charge for the cation (e.g., Na+, Mg2+).

• Type II: More than one possible charge for the cation (e.g., Fe2+ and Fe3+).

Type I Cations:

• Alkali metals (Group 1A): +1 cation

• Alkaline earth metals (Group 2A): +2 cation

• Polyatomic cations (e.g., NH4+): only one possible charge

Type II Cations:

• Transition metals (Groups 3-12): often form more than one type of cation

Naming Type I Ionic Compounds

For Type I compounds, the cation is named first, followed by the anion. The cation name is the same as the element. The anion is named by taking the root of the element and adding the suffix -ide.

• Example: MgF2 is named magnesium fluoride.

For compounds with polyatomic ions, memorize the names of the ions. No prefixes or suffixes are added.

Naming Type II Ionic Compounds

For Type II compounds, use a Roman numeral after the cation to indicate its charge.

• Example: FeO is iron(II) oxide; Fe2O3 is iron(III) oxide.

Alternatively, traditional names use the suffix -ous for the lower charge and -ic for the higher charge.

• Example: FeO is ferrous oxide; Fe2O3 is ferric oxide.

Table: Common Type II Cations and Their Traditional Names

Naming Binary Covalent Compounds

Identifying Binary Covalent Compounds

Binary covalent compounds contain only nonmetals. If a compound contains only nonmetals (and is not a polyatomic ion), it is likely covalent.

• Example: CO2 (carbon dioxide), H2O (water)

Note: Some compounds with only nonmetals are ionic if they contain polyatomic ions (e.g., NH4Br).

Naming Binary Covalent Compounds

The first element is named first. The second element is named as if it were an anion (root + -ide). Prefixes are used to denote the number of each atom present. The prefix mono- is never used for the first element.

• Prefix Table:

• Example: P2O5 is diphosphorus pentoxide.

Naming Acids

Identifying Acids

Acids are compounds that produce H+ ions in water. If hydrogen is written first in the formula, the compound is usually an acid.

• Binary Acids: Contain hydrogen and a nonmetal (usually a halogen or sulfur).

• Oxyacids: Contain hydrogen, oxygen, and another element (usually a polyatomic ion).

Naming Binary Acids

Binary acids are named using the prefix hydro-, the root of the nonmetal, the suffix -ic, and the word acid.

• Example: HCl is hydrochloric acid.

Common Binary Acids:

Naming Oxyacids

Oxyacids are named based on the polyatomic ion present:

• If the anion ends in -ate, the acid name ends in -ic acid.

• If the anion ends in -ite, the acid name ends in -ous acid.

• If the anion has a prefix (e.g., hypo-, per-), retain the prefix in the acid name.

• Example: HNO3 (from nitrate, NO3-) is nitric acid.

• Example: HNO2 (from nitrite, NO2-) is nitrous acid.

Additional info:

• For polyatomic ions, the number of hydrogens added to the ion equals the charge on the anion (e.g., H2SO4 for SO42-).

• Some elements (N, P, O) do not form binary acids with hydrogen.