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

Chapter 2: Atoms, Molecules, and Ions

Monatomic & Polyatomic Ions / Cations / Halo-anions

This section introduces the concept of ions, which are charged species formed when atoms gain or lose electrons. Ions are classified as monatomic (single atom) or polyatomic (multiple atoms bonded together).

• Monatomic ions: Ions consisting of a single atom, e.g., Na+, Cl-.

• Polyatomic ions: Ions composed of two or more atoms covalently bonded, e.g., SO42-, NH4+.

• Cations: Positively charged ions (loss of electrons).

• Anions: Negatively charged ions (gain of electrons).

• Halo-anions: Anions derived from halogens, e.g., F-, Br-.

Example: The sulfate ion (SO42-) is a polyatomic anion commonly found in salts.

Nomenclature of Ionic Compounds (Including 'ing')

Naming ionic compounds follows specific rules based on the type of ions involved.

• Binary ionic compounds: Name the cation first, then the anion (e.g., NaCl is sodium chloride).

• Polyatomic ions: Use the name of the polyatomic ion as is (e.g., Na2SO4 is sodium sulfate).

• Transition metals: Indicate the charge with Roman numerals (e.g., FeCl3 is iron(III) chloride).

Example: Ca(NO3)2 is calcium nitrate.

Nomenclature of Molecular Compounds

Molecular compounds are named using prefixes to indicate the number of atoms.

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

• First element: Use the full name.

• Second element: Use the root and add '-ide'.

Example: CO2 is carbon dioxide.

Alkanes with Alkyl / Alkyl Halides Substituents

Alkanes are saturated hydrocarbons. Substituents such as alkyl groups or halides can replace hydrogen atoms.

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

• Alkyl halide: An alkane with a halogen substituent (e.g., chloromethane).

Example: CH3CH2Br is bromoethane.

Cycloalkanes with Alkyl / Alkyl Halides Substituents

Cycloalkanes are ring-shaped alkanes. Substituents can be attached to the ring structure.

• Cycloalkane: Hydrocarbon with a ring structure (e.g., cyclopentane).

• Substituents: Named and numbered according to IUPAC rules.

Example: 1-chlorocyclohexane is a cyclohexane ring with a chlorine substituent at position 1.

Structural Isomers

Structural isomers are compounds with the same molecular formula but different connectivity of atoms.

• Isomerism: Occurs when compounds have the same formula but different structures.

• Types: Chain isomerism, position isomerism, functional group isomerism.

Example: C4H10 can be butane or isobutane.

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

Functional groups such as alcohols and carboxylic acids can be attached to hydrocarbon chains or rings, altering their chemical properties.

• Alcohol group (-OH): Present in ethanol (CH3CH2OH).

• Carboxylic acid group (-COOH): Present in acetic acid (CH3COOH).

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

Example: Benzoic acid is benzene with a carboxylic acid group.

Additional info: The study guide covers foundational nomenclature and classification topics relevant to Chapter 2 of General Chemistry, including ions, molecular compounds, isomerism, and functional groups. These concepts are essential for understanding chemical formulas, reactions, and properties.