Principles of Chemistry: Key Concepts

Cations

• Formed when an atom loses electrons from its valence shell.
• Positively charged (more protons than electrons).
• Example: Mg forms Mg²⁺ by losing 2 electrons.

Anions

• Formed when an atom gains electrons into its valence shell.
• Negatively charged (more electrons than protons).
• Example: F forms F⁻ by gaining an electron.

Periodic Table Overview

• Developed by Dmitri Mendeleev; properties are periodic functions of atomic mass.
• Modern periodic law: Properties are periodic functions of atomic numbers.

Major Areas of the Periodic Table

• Metals (main group, transition, inner transition)
• Metalloids
• Nonmetals

Characteristics of Metals

• Solid at room temperature (except Hg).
• Shiny, conductive (heat and electricity).
• Malleable and ductile.
• Form cations.

Characteristics of Metalloids

• Exhibit properties of metals/nonmetals.
• Semiconductors (poor heat conductors).

Characteristics of Nonmetals

• Found in gas, liquid, and solid states.
• Poor conductors; solid nonmetals are brittle.
• Gain electrons to form anions.

Chemical Bonds

• Compounds are formed by chemical bonds: ionic, covalent, and metallic.
• Ionic bonds: metal + nonmetal, transfer of electrons.
• Covalent bonds: nonmetals sharing electrons.

Ionic Compounds

• Formed from cations and anions.
• Formula is neutral (net charge of zero).
• Commonly contain simple or polyatomic ions.

Common Oxidation States

• Alkali metals: +1, Alkaline earth metals: +2.
• Halogens: -1, 5A nonmetals: -3, 6A nonmetals: -2.

Naming Ionic Compounds

• Metal name first, nonmetal name with "-ide" ending.
• Transition metals indicate oxidation state with Roman numerals.

Hydrated vs. Anhydrous Compounds

• Hydrates contain specific water molecules; indicated with prefixes (e.g., hexahydrate).

Naming Molecular Compounds

• Nonmetal names use prefixes for number of atoms.
• Example: CO₂ = carbon dioxide, SBr₆ = sulfur hexabromide.