Chemical Bonds Overview

Chemical Bonds

• Chemical bonds are classified into three types based on the atoms involved: ionic, covalent, and metallic.

• Ionic bond: Forms when electrons are transferred between atoms, creating oppositely charged ions that attract each other. Generally forms when a metal bonds with a nonmetal. The method is electron transfer.

• Covalent bond: Forms when two atoms share some of their electrons. Generally forms when nonmetal atoms bond together. The method is electron sharing.

• Metallic bond: Forms when metal and metal atoms bond. Electrons are pooled.

• Types of Atoms and Corresponding Bonds:

  • Metal and nonmetal → Ionic bond
  • Nonmetal and nonmetal → Covalent bond
  • Metal and metal → Metallic bond

The Ionic Bond

• Ionic bonds form when electrons are transferred between atoms, creating oppositely charged ions.
• This usually happens when a metal bonds to a nonmetal.
• The method is electron transfer. This results in a compound with a crystalline lattice structure.
• Ions formed are called cations (positive) and anions (negative).

The Covalent Bond

• Covalent bonds form when atoms share electrons.
• This typically occurs between nonmetal atoms.
• The shared electrons hold the atoms together by attracting the nuclei of both.
• The method is electron sharing.
• Covalent bonds can be single, double, or triple, depending on how many electron pairs are shared.
  • Single covalent bond: one electron pair shared (2 electrons)
  • Double covalent bond: two electron pairs shared (4 electrons)
  • Triple covalent bond: three electron pairs shared (6 electrons)

The Coordinate Bond

• A coordinate bond, also called a dative covalent bond, is a covalent bond where both electrons originate from the same atom.
• One atom (donor/Lewis base) provides a lone pair of electrons, and another atom (acceptor/Lewis acid) accepts them.
• Lewis acid: electron pair acceptor
• Lewis base: electron pair donor

Representing Valence Electrons (Lewis Structures)

• Lewis structures are diagrams that show valence electrons in main group elements as dots.
• The number of valence electrons is equal to the group number in the periodic table (except for helium).
• Dots are placed around the element's symbol, with a maximum of two dots per side initially. Single dots are placed first before pairing.

Intermolecular Forces

• Intermolecular forces are the attractive forces between molecules.
• They are generally much weaker than the intramolecular forces holding atoms together within a molecule.
• These forces influence various physical properties:
  • Melting and boiling points
  • Solubility
  • Rate and outcome of chemical reactions

Intermolecular Forces in Covalent Molecules

• Three types of intermolecular forces in covalent molecules, ranked by increasing strength:
  • London dispersion forces: Very weak forces caused by temporary changes in electron density. Strength increases with molecular size.
  • Dipole-dipole interactions: Moderate forces between permanent dipoles in polar molecules. Dipoles align so that opposite charges are close.
  • Hydrogen bonding: Strong forces between molecules where a hydrogen atom bonded to a highly electronegative atom (O, N, or F) is attracted to another electronegative atom in another molecule.

Ion-Dipole Forces

• Ion-dipole forces are electrostatic attractions between a charged ion and a polar molecule.
• These forces are common in solutions, particularly for ionic compounds dissolving in polar solvents like water.
• The strength of the ion-dipole interaction is proportional to:
  • The charge on the ion
  • The magnitude of the dipole moment of the molecule.

This quiz covers the different types of chemical bonds, including ionic, covalent, and metallic bonds. Understand how these bonds form based on the types of atoms involved and the methods of electron transfer or sharing. Test your knowledge of the fundamental concepts of chemical bonding.