Ions and Ionic Compounds

Formation of Ions

Atoms form ions by gaining or losing electrons to achieve a stable electron configuration, often resembling that of noble gases.

• Cations: Positively charged ions formed when atoms lose electrons (typically metals).

• Anions: Negatively charged ions formed when atoms gain electrons (typically nonmetals).

• Example: Sodium (Na) loses one electron to form Na+; chlorine (Cl) gains one electron to form Cl-.

Electron Gain and Loss in Common Elements

• Aluminum (Al): Loses 3 electrons to form Al3+.

• Chlorine (Cl): Gains 1 electron to form Cl-.

• Sodium (Na): Loses 1 electron to form Na+.

Symbolism for Ions

• Ion Notation: The symbol for an ion includes its charge as a superscript (e.g., K+, Ca2+).

• Example: An atom with 19 protons and 18 electrons is K+ (potassium ion).

Properties of Ions

• Anions always have a negative charge.

• Cations always have a positive charge.

Formulas and Naming of Ionic Compounds

Writing Formulas for Ionic Compounds

Ionic compounds are formed from cations and anions in ratios that produce a neutral overall charge.

• Example: Magnesium chloride is MgCl2 (Mg2+ and two Cl-).

• Oxide ion: O2-

• Compound with Na+ and PO43-: Na3PO4

Naming Ionic Compounds

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

• Transition Metals: Use Roman numerals to indicate charge (e.g., FeSO4 is iron(II) sulfate).

• Polyatomic Ions: Compounds containing polyatomic ions retain the ion's name (e.g., NaNO3 is sodium nitrate).

Common Polyatomic Ions

Covalent (Molecular) Compounds

Formation and Naming

Covalent compounds are formed when two or more nonmetals share electrons.

• Prefixes are used to indicate the number of atoms (e.g., CO2 is carbon dioxide).

• Examples: N2O3 is dinitrogen trioxide; CCl4 is carbon tetrachloride.

Diatomic Molecules

• Diatomic Elements: H2, N2, O2, F2, Cl2, Br2, I2

• Example: Carbon does not exist as a diatomic molecule.

Bond Types and Polarity

Ionic vs. Covalent Bonds

• Ionic Bonds: Formed between metals and nonmetals; involve transfer of electrons.

• Covalent Bonds: Formed between nonmetals; involve sharing of electrons.

• Example: CaO contains an ionic bond; H2O contains polar covalent bonds.

Polarity of Molecules

• Electronegativity: Determines bond polarity; higher difference leads to more polar bonds.

• Polar Molecules: Have an uneven distribution of charge (e.g., NH3, H2O).

• Nonpolar Molecules: Have an even distribution of charge (e.g., CO2).

• Example: The bond between H and O is polar covalent; CO2 is linear and nonpolar.

Intermolecular Forces

Types of Intermolecular Forces

• Dispersion Forces: Present in all molecules, especially nonpolar ones (e.g., Cl2).

• Dipole-Dipole Attractions: Occur between polar molecules (e.g., HBr).

• Hydrogen Bonds: Strongest type, occur when H is bonded to N, O, or F (e.g., NH3).

Summary Table: Key Concepts

Important Formulas and Equations

• General Ionic Compound Formula:

• Example for Magnesium Chloride:

• Example for Sodium Phosphate:

Additional info:

• Some questions and answers were inferred to provide complete academic context and explanations.

• All key terms and examples are relevant to GOB Chemistry and suitable for college-level study.