Naming and Formula Writing of Acids, Ionic, and Covalent Compounds

Rules for Naming Ions

In chemistry, the process of naming ions is crucial for understanding compound structure and behavior. Ions are formed when atoms gain or lose electrons, resulting in a positive or negative charge.

Metal Ions: When metals lose electrons, they become positively charged ions known as cations. Notably, the name of the metal does not change when it becomes an ion. For example:

Na → Na⁺ + e⁻ (sodium remains sodium)

Nonmetal Ions: In contrast, when nonmetals gain electrons, they become negatively charged ions called anions. The naming convention involves modifying the nonmetal's name with the addition of the suffix -ide. For example:

F + e⁻ → F⁻ (fluorine changes to fluoride)

Naming Ionic Compounds

Steps for Naming Binary Ionic Compounds

Naming ionic compounds involves a systematic approach. The following steps are typically followed:

Write the name of the metal ion.
Write the name of the nonmetal ion.

Examples of binary ionic compounds include:

CaO = calcium oxide
Li₂S = lithium sulfide
KI = potassium iodide

Naming Binary Ionic Compounds with Variable Charge (Stock Method)

For metals that can form more than one type of cation, the Stock method is utilized. The steps include:

Determine the charge of the cation based on the subscript of the anion.
Name the cation by its element name, adding a Roman numeral in parentheses to indicate its charge.
Write the anion with the suffix -ide.

Examples include:

Cr₂O₃ = chromium (III) oxide
SnCl₄ = tin (IV) chloride
Cu₃N = copper (I) nitride

Naming Binary Ionic Compounds with Variable Charge (Classical Method)

The classical method differs slightly from the Stock method. The steps are as follows:

Determine the charge of the cation based on the anion's subscript.
Use the Latin name for the cation. The lower charge ends with -ous, and the higher charge ends with -ic.
Write the anion with the -ide suffix.

Examples include:

Cr₂O₃ = chromic oxide
SnCl₄ = stannic chloride
Cu₃N = cuprous nitride

Formula Writing for Ionic Compounds

Steps for Writing the Formula of Binary Ionic Compounds

The formula for binary ionic compounds can be derived through a series of steps:

Write the symbol of the metal ion.
Write the symbol of the nonmetal ion.
Determine their charges using the periodic table.
Crisscross the charges to write them as subscripts for the respective ions.
Reduce to the lowest terms if necessary.

For instance, magnesium iodide can be represented as:

Mg²⁺ + I⁻ → MgI₂

Steps for Writing the Formula of Binary Ionic Compounds with Variable Charge

The process is similar but accounts for the variable charge, as follows:

Write the symbol of the cation.
Write the symbol of the anion.
Determine the charges from the periodic table and the Roman numeral.
Crisscross the charges and write them as subscripts.

Example:

Iron (III) oxide can be represented as:
Fe³⁺ + O²⁻ → Fe₂O₃

Covalent Compounds

Naming Binary Covalent Compounds

When dealing with covalent compounds, different rules apply, particularly geared towards nonmetals:

Write the name of the first nonmetal.
Write the name of the second nonmetal, changing its ending to -ide.
Add prefixes as necessary to indicate the number of each element present in the compound.

Examples include:

N₂O₄ = dinitrogen tetroxide
CO₂ = carbon dioxide
P₂S₅ = diphosphorus pentasulfide

Writing the Formula of Binary Covalent Compounds

The formation of the formula for binary covalent compounds aligns with these steps:

Write the symbol of the first nonmetal along with the corresponding subscript based on the prefix.
Write the symbol of the second nonmetal with the appropriate subscript based on its prefix.

For instance, dinitrogen tetrafluoride can be written as:

N₂F₄

Ternary Compounds

Naming Ternary Compounds

Ternary compounds contain multiple types of ions, including polyatomic ions. The naming of these compounds involves using the name of the polyatomic ion directly:

Examples include:

NH₄F = ammonium fluoride
Mg(NO₃)₂ = magnesium nitrate
NaOH = sodium hydroxide

Writing the Formula of Ternary Compounds

The writing of formulas for ternary compounds also requires a systematic approach:

Write the symbol for the metal ion.
Write the formula of the polyatomic ion.
Determine the respective charges using the periodic table and the polyatomic ion table.
Crisscross the charges and write them as subscripts.
Reduce to lowest terms if necessary.

For example:

Sr²⁺ + NO₃⁻ → Sr(NO₃)₂

Rules for Naming Acids

Acids without Oxygen

When the anion in the acid does not contain oxygen, the naming convention involves adding the prefix 'hydro-' to the root name of the element and adding the suffix '-ic'. For example:

HCl = hydrochloric acid
HCN = hydrocyanic acid
H₂S = hydrosulfuric acid

Acids with Oxygen

When the anion contains oxygen, the name is derived from the root name of the anion:

If the anion ends in -ate, the acid name will use the suffix -ic.

Examples include:
H₂SO₄ = sulfuric acid, where the anion is SO₄²⁻ (sulfate).
H₃PO₄ = phosphoric acid, where the anion is PO₄³⁻ (phosphate).

If the anion ends in -ite, the acid name will use the suffix -ous.

Examples include:
H₂SO₃ = sulfurous acid, where the anion is SO₃²⁻ (sulfite).
HNO₂ = nitrous acid, where the anion is NO₂⁻ (nitrite).

Comprehensive Guide to Naming and Formula Writing of Compounds

Comprehensive Guide to Naming and Formula Writing of Compounds