General Chemistry Study Guide: Chapter 2 – Atoms, Molecules, and Ions

Chapter 2: Atoms, Molecules, and Ions

Monatomic & Polyatomic Ions: Cations / Anions / Halo-anions

This section covers the basic types of ions found in chemistry, including their definitions and examples.

• Monatomic ions: Ions consisting of a single atom with a positive (cation) or negative (anion) charge. Example: $\text{Na}^+$ (sodium ion), $\text{Cl}^-$ (chloride ion)

• Polyatomic ions: Ions composed of two or more atoms covalently bonded, carrying a net charge. Example: $\text{SO}_4^{2-}$ (sulfate ion), $\text{NO}_3^-$ (nitrate ion)

• Halo-anions: Polyatomic ions containing halogens, such as $\text{ClO}_4^-$ (perchlorate ion).

Nomenclature of Ionic Compounds (Including Naming Rules)

Naming ionic compounds involves identifying the cation and anion and applying systematic rules.

• Cations: Named first; for metals with variable charges, the charge is indicated in Roman numerals. Example: $\text{FeCl}_2$ is iron(II) chloride.

• Anions: Named by replacing the ending of the element with “-ide” for monatomic anions. Example: $\text{NaCl}$ is sodium chloride.

• Polyatomic ions: Use the common name (e.g., sulfate, nitrate).

Nomenclature of Molecular Compounds

Molecular compounds are named using prefixes to indicate the number of each atom present.

• Prefixes: mono-, di-, tri-, tetra-, penta-, etc.

• Example: $\text{CO}_2$ is carbon dioxide; $\text{N}_2\text{O}_4$ is dinitrogen tetroxide.

Alkanes with Alkyl / Alkyl Halides Substituents

Alkanes are saturated hydrocarbons. Substituents such as alkyl groups or halides modify their structure and properties.

• Alkyl group: A hydrocarbon group derived from an alkane by removing one hydrogen atom (e.g., methyl, ethyl).

• Alkyl halides: Compounds where one or more hydrogen atoms in an alkane are replaced by halogen atoms (e.g., chloromethane, $\text{CH}_3\text{Cl}$).

Cycloalkanes with Alkyl / Alkyl Halides Substituents

Cycloalkanes are ring-shaped alkanes. They can have alkyl or halide substituents attached to the ring.

• Example: Methylcyclohexane ($\text{C}_6\text{H}_{11}\text{CH}_3$), bromocyclopentane ($\text{C}_5\text{H}_9\text{Br}$).

Nomenclature: Summary

Nomenclature rules are essential for clear communication in chemistry. They allow chemists to deduce the structure and composition of compounds from their names.

• Follow IUPAC rules for systematic naming.

• Use prefixes and suffixes to indicate the number and type of atoms or groups present.

Natural Isomers

Isomers are compounds with the same molecular formula but different structures or arrangements of atoms.

• Structural isomers: Differ in the connectivity of atoms.

• Stereoisomers: Same connectivity but different spatial arrangement.

• Example: Butane ($\text{C}_4\text{H}_{10}$) and isobutane are structural isomers.

Alkanes, Cycloalkanes, Benzene with Alcohol & Carboxylic Acid Functional Groups

Functional groups define the chemical properties of organic molecules. Alcohols and carboxylic acids are common functional groups attached to hydrocarbon chains or rings.

• Alcohols: Contain the hydroxyl group ($-\text{OH}$). Example: Ethanol ($\text{CH}_3\text{CH}_2\text{OH}$).

• Carboxylic acids: Contain the carboxyl group ($-\text{COOH}$). Example: Acetic acid ($\text{CH}_3\text{COOH}$).

• Benzene derivatives: Aromatic compounds with functional groups attached to the benzene ring.

Additional info: This study guide covers foundational concepts in chemical nomenclature, ion classification, and basic organic chemistry relevant to General Chemistry. For further study, refer to IUPAC nomenclature guidelines and practice naming exercises.