Chemistry Chapter 8: Covalent Bonding Flashcards

Covalent Bonding Overview

• Covalent bonds are formed when atoms share electrons, leading to stable molecular structures.
• A molecule is defined as a neutral group of atoms bonded covalently.

Molecules & Molecular Compounds

• Diatomic molecules consist of two atoms, while molecular compounds are formed from different elements held together by covalent bonds, such as water.
• Molecular formulas represent the number of each type of atom in a molecule; for example, the molecular formula of water is H₂O.

Bond Types and Characteristics

• Single covalent bonds involve sharing one pair of electrons; double and triple bonds involve two or three pairs, respectively.
• Coordinate covalent bonds occur when one atom provides both electrons for the bond, represented with arrows.
• Characteristics of molecular compounds include lower melting and boiling points compared to ionic compounds and a tendency to exist as gases or liquids at room temperature.

Electron Configuration

• Atoms in covalent bonds aim for noble gas electron configurations through electron sharing, often forming double or triple bonds.
• Carbon typically forms four covalent bonds, while halogens form single bonds in diatomic molecules.

Structural Representations

• Structural formulas use dashes to represent covalent bonds and illustrate the arrangement of atoms.
• Resonance structures depict molecules that can be represented by two or more valid dot structures with equivalent electron arrangements.

Molecular Geometry

• VSEPR theory explains molecular shapes based on the repulsion between electron pairs.
• The tetrahedral angle of molecular geometry is approximately 109.5 degrees.

Polar and Nonpolar Bonds

• Covalent bonds may be nonpolar (equal sharing of electrons, e.g., diatomic elements) or polar (unequal sharing, leading to partial charges).
• The distribution of charges in polar bonds is determined by the differences in electronegativity between atoms.

Intermolecular Forces

• Intermolecular attractions are weaker than ionic or covalent bonds but influence the states of matter—solid, liquid, or gas.
• Van der Waals forces include dipole interactions (attractions between polar molecules) and dispersion forces (weak attractions between nonpolar molecules).
• Hydrogen bonds are specific interactions where hydrogen attached to electronegative atoms (like O, N, or F) is attracted to unshared electron pairs from other electronegative atoms.

Physical Properties of Covalent Compounds

• Covalent compounds often have low melting and boiling points due to weak intermolecular forces.
• Network solids are an exception, being strong, stable substances that require high temperatures (above 1000 degrees) to melt due to extensive covalent bonding throughout the structure.