Classification and Nomenclature of Inorganic Compounds and Acids

Guida di studio - Note intelligenti

Appunti personalizzati basati sui tuoi materiali, ampliati con definizioni chiave, esempi e contesto.

Language of Chemistry: Classification and Nomenclature

Overview of Inorganic Compounds and Acids

Inorganic compounds are classified based on their composition and bonding. Most inorganic compounds do not contain carbon, with exceptions such as carbon dioxide and carbonates. The International Union of Pure and Applied Chemistry (IUPAC) sets the rules for naming these compounds, ensuring systematic and universal nomenclature.

Classification of inorganic compounds and acids

Classes of Inorganic Compounds

There are five common classes of inorganic compounds:

Binary Ionic Compounds: Composed of a metal and a nonmetal (e.g., NaCl, CaO).
Ternary Ionic Compounds: Contain a metal, a nonmetal, and oxygen (e.g., KNO3, CaCO3).
Binary Molecular Compounds: Composed of two nonmetals (e.g., NH3, SO2).
Binary Acids: Aqueous solutions of hydrogen and a nonmetal (e.g., HCl(aq)).
Ternary Oxyacids: Aqueous solutions of hydrogen, oxygen, and another nonmetal (e.g., HNO3(aq)).

Example of binary molecular compound P4S3 Example of binary acid HF

Classification of Ions

Types of Ions

An ion is an atom or group of atoms with a charge. Ions are classified as:

Cations: Positively charged ions (e.g., Na+, NH4+).
Anions: Negatively charged ions (e.g., Cl–, SO42–).
Monoatomic: Single atom ions (e.g., Na+, Cl–).
Polyatomic: Group of atoms with a charge (e.g., NH4+, CO32–).

Classification of ions Example of polyatomic ion (NH4)2CO3

Common Monoatomic Anions

Monoatomic anions are named by adding the suffix -ide to the root name of the element.

Anion	IUPAC Name	Anion	IUPAC Name
Br–	bromide ion	N3–	nitride ion
Cl–	chloride ion	O2–	oxide ion
F–	fluoride ion	P3–	phosphide ion
I–	iodide ion	S2–	sulfide ion

Table of common monoatomic anions

Predicting Charges of Monoatomic Ions

The charge of a metal ion from representative elements (A groups) is equal to the family number. For anions, the charge is the family number minus eight.

Formula:

Periodic table showing common monoatomic ion charges

Common Polyatomic Ions

Polyatomic ions often contain oxygen and are called oxyanions. The suffix -ate indicates more oxygen atoms, while -ite indicates fewer. Some exceptions use -ide (e.g., hydroxide, cyanide).

Cation	IUPAC Name	Anion	IUPAC Name
NH4+	ammonium ion	C2H3O2–	acetate ion
		CO32–	carbonate ion
		OH–	hydroxide ion
		NO3–	nitrate ion
		SO42–	sulfate ion
		PO43–	phosphate ion

Table of common polyatomic ions

Writing Chemical Formulas

Formulas of Ionic Compounds

An ionic compound is composed of positive and negative ions. The formula unit is neutral, so the total positive charge must equal the total negative charge.

If charges are equal: one of each ion (e.g., Ca2+ and O2– form CaO).
If charges are not equal: balance charges with subscripts (e.g., Ba2+ and Cl– form BaCl2).

Example of writing formulas for binary ionic compounds

Formulas with Polyatomic Ions

Follow the same rules as binary ionic compounds. If more than one polyatomic ion is needed, use parentheses (e.g., (NH4)2SO4).

Naming Ionic and Molecular Compounds

Naming Binary Ionic Compounds

Combine the cation and anion names, dropping the word "ion." The cation is named first, followed by the anion with the suffix -ide.

Example of binary ionic compound HgS

Naming Binary Molecular Compounds

Binary molecular compounds are composed of two nonmetals. The first element is named first, and the second element has the suffix -ide. The number of atoms is indicated by Greek prefixes.

Atoms	Prefix	Atoms	Prefix
1	mono–	6	hexa–
2	di–	7	hepta–
3	tri–	8	octa–
4	tetra–	9	nona–
5	penta–	10	deca–

Table of Greek prefixes for binary molecular compounds

Example: Naming P4S3

P4S3 is named tetraphosphorus trisulfide, using the prefixes tetra– and tri–.

Naming Acids

Binary Acids

A binary acid is an aqueous solution of hydrogen and a nonmetal. The formula begins with H. Binary acids are named using the prefix hydro– and the suffix -ic acid (e.g., HF(aq) is hydrofluoric acid).

Example of binary acid HF

Ternary Oxyacids

Ternary oxyacids are aqueous solutions of hydrogen and an oxyanion. If the acid is derived from an oxyanion ending in -ate, the suffix is changed to -ic acid (e.g., HNO3(aq) is nitric acid). If derived from -ite, the suffix is changed to -ous acid (e.g., HNO2(aq) is nitrous acid).

Ternary	Oxyacid	Ternary	Compound
HClO	hypochlorous acid	NaClO	sodium hypochlorite
HClO2	chlorous acid	NaClO2	sodium chlorite
HClO3	chloric acid	NaClO3	sodium chlorate
HClO4	perchloric acid	NaClO4	sodium perchlorate

Table of ternary oxyacids and related compounds

Summary of Key Points

Most inorganic compounds do not contain carbon.
Binary ionic compounds: metal + nonmetal.
Ternary ionic compounds: metal + nonmetal + oxygen.
Binary molecular compounds: two nonmetals.
Acids: hydrogen + nonmetal or oxyanion.
Cations: element name + "ion"; variable charge indicated by Roman numerals.
Ionic compounds: cation first, anion second, anion ends with -ide.
Molecular compounds: Greek prefixes indicate number of atoms.
Binary acids: hydro– + element stem + -ic acid.
Ternary oxyacids: -ate becomes -ic acid, -ite becomes -ous acid.