Chemistry Notes on Ionic and Covalent Compounds

Missing Material and Test Preparation

  • Missing Page 23: The teacher plans to print it and distribute it later.

  • Practice Importance: Checking each student's understanding can be helpful, but today’s quiz served as practice.

Review of Ionic and Covalent Compounds

  • Ionic Compounds:

    • Definition: Formed between metals and nonmetals (a cation and an anion).

    • Charge Exchange: Involves the transfer of electrons.

    • Characteristics: High melting and boiling points, can conduct electricity when dissolved in water.

  • Covalent Compounds:

    • Definition: Formed between nonmetals that share electrons; both are found on the right side of the periodic table.

    • Molecule Formation: A molecule consists of two or more elements covalently bonded.

    • Bond Types: Bonds can be single, double, or triple based on the number of shared electron pairs.

    • Electron Sharing: No transfer occurs; they share electrons, which will be illustrated through molecular structures in the upcoming lessons.

Examples of Bonds

  • Single Bond Example:

    • Hydrogen Molecule (H): Two hydrogen atoms share one pair of electrons.

    • Structure Representation: The shared pair is represented by a bar as

    • H - H

  • Double Bond Example:

    • Oxygen Molecule (O e2): Two oxygen atoms share two pairs of electrons.

    • Structure: O=O (two lines for two shared pairs).

    • Carbon Dioxide (CO e2): Carbon shares with two oxygen atoms, having a double bond with each.

Drawing Molecular Structures

  • Diatomic Elements: Certain elements never exist alone; they always come in pairs such as:

    • H, N, O, F, Br, I

  • Valence Electrons:

    • Hydrogen: One valence electron; can form a bond with another hydrogen.

    • Oxygen: Six valence electrons, needs two bonds to satisfy the octet rule.

  • Central Atoms:

    • Carbon often serves as the central atom in molecular structures; it can form four bonds.

Properties of Covalent Compounds

  • Typically have low melting and boiling points.

  • Cannot conduct electricity in solution, unlike ionic compounds.

Naming Covalent Compounds

  • Naming Methodology:

    • First element with a prefix (unless there's only one), second always with a prefix.

    • Example: Carbon Dioxide (CO
      e2) = one carbon and two oxygens.

  • Prefixes:

    • Mono- (1), Di- (2), Tri- (3), Tetra- (4), Penta- (5), Hexa- (6), Hepta- (7), Octa- (8), Nona- (9), Deca- (10).

Writing Chemical Formulas

  • Determine subscripts based on prefixes.

  • Example: Dichlorine monoxide (Cl e2O)

    • Di- indicates two chlorines, mono- indicates one oxygen.

  • Note that there are no charges with covalent compounds, unlike ionic compounds, meaning no polyatomic ions.

Important Considerations

  • Structure Drawing Practice: Students are encouraged to sketch bonds while learning.

  • Prefixes must be memorized for proper naming and formula writing.

Upcoming Tests

  • Scheduled Tests: There are two tests covering ionic and covalent compounds.

  • Preparation Focus: Emphasis will be placed on details during review and practice sessions ahead of the tests.