Chapter 3_CHEMICAL BONDS_Molecule Formation_released

Chapter 3: Chemical Bonds - Molecule Formation

Chapter Objectives

• By the end of this chapter, you should be able to:

  • 3.1: Draw correct Lewis dot structures for atoms of the representative elements. (Section 3.1)

  • 3.2: Use electron configurations to determine the number of electrons gained or lost by atoms to achieve noble gas configurations. (Section 3.2)

  • 3.3: Use electron configurations to determine ions that are isoelectronic with noble gases. (Section 3.2)

  • 3.4: Use the octet rule to predict ions formed during the formation of ionic compounds. (Section 3.3)

  • 3.5: Write correct formula units for ionic compounds containing a representative metal and a representative nonmetal. (Section 3.3)

  • 3.6: Determine formula weights for ionic compounds in atomic mass units. (Section 3.3)

  • 3.7: Correctly name binary ionic compounds. (Section 3.4)

  • 3.8: Draw correct Lewis structures for covalent molecules. (Section 3.5)

  • 3.9: Determine molecular weights for covalent compounds in atomic mass units. (Section 3.5)

  • 3.10: Correctly name binary covalent compounds. (Section 3.6)

  • 3.11: Draw correct Lewis structures for polyatomic ions. (Section 3.7)

  • 3.12: Write correct formulas for ionic compounds containing representative metals and polyatomic ions. (Section 3.8)

  • 3.13: Correctly name binary ionic compounds containing polyatomic ions. (Section 3.8)

Lewis Dot Structures

• Definition: A Lewis dot structure is a representation of an atom or ion, where the elemental symbol represents the atomic nucleus and non-valence electrons, while valence electrons are shown as dots.

• Example: For sodium (Na), the abbreviated electron configuration is [Ne]3s1 resulting in the Lewis dot structure Na·.

Formation of Ions

• Octet Rule: Atoms gain, lose, or share electrons to achieve electron configuration similar to a noble gas (eight electrons in the valence shell).

• Types of Ions:

  • Cation: Atom with a net positive charge due to loss of electrons.

  • Anion: Atom with a net negative charge due to gaining electrons.

Isoelectronic Series

• Definition: Atoms or ions with identical electron configurations.

• Example: When sodium loses one electron to form Na+, it becomes isoelectronic with Neon (Ne), although Na+ differs from Ne in the number of protons.

Ionic Compounds

• Ionic Bond: The attractive force that holds oppositely charged ions together.

• Formula Unit: The simplest ratio of ions in an ionic compound.

• Example of reaction: Sodium loses an electron to chlorine, forming NaCl, where both ions achieve full octets.

Naming Binary Ionic Compounds

• Definition: A binary compound consists of two different elements.

• Naming Format: metal + nonmetal stem + -ide (e.g., NaCl -> sodium chloride).

• Metal Cations with Multiple Charges: Must indicate ion type with a Roman numeral (e.g., CuCl2 is copper(II) chloride).

Covalent Bonds

• Formed when nonmetals share electrons due to their inability to lose or gain electrons easily.

• Covalent Compound: Formed by the sharing of electrons between two nonmetals.

Drawing Lewis Structures**

• Steps:

  1. Determine number of atoms of each element from the molecular formula.

  2. Count total valence-shell electrons.

  3. Arrange with least electronegative atom in the center.

  4. Connect atoms with single bonds and add remaining electrons to complete octets.

  5. If necessary, move lone pairs to form double or triple bonds.

Naming Binary Covalent Compounds

• Rules:

  1. Name the less electronegative element first.

  2. Use the stem of the more electronegative element, adding -ide.

  3. Indicate the number of each type of atom with Greek prefixes (mono-, di-, tri-, etc.).

Polyatomic Ions

• Definition: Groups of covalently bonded atoms with a net charge.

• Examples of common polyatomic ions include:

  • NH4+ (ammonium)

  • SO4^2- (sulfate)

• Lewis Structures for Polyatomic Ions: Adjust the number of total electrons based on the charge (add for negative, subtract for positive).

Summary of Chapter Objectives

• Review all chapter objectives to ensure understanding and readiness for concepts related to Lewis structures, ionic compounds, and covalent bonding.