Understanding Chemical Bonds: Types, Properties, and Examples

Understanding Chemical Bonds

Link: Union of two or more atoms to form larger entities such as molecules or elements.

Types of Chemical Bonds

Ionic Bond: Union between ions of different signs.

  • Occurs when the electronegativity difference is greater than 1.7.
  • Typically between a metal and a nonmetal.
  • Example: Group IIA + O

Covalent Bond: Forms when the electronegativity difference is not sufficient to transfer electrons from atoms. Atoms share one or more pairs of electrons in an orbital.

Metallic Bond: A chemical bond that holds the atoms of metals together.

Key Concepts in Chemical Bonding

Octet Rule: A rule to explain bonding between atoms, stating that when forming a chemical bond, atoms acquire, assign, or share electrons to have the same number of electrons in their last layer.

Exceptions to the Octet Rule: In some compounds, the number of electrons surrounding the central atom in a stable molecule is less than 8.

Molecules with an Odd Number of Electrons: Some molecules with an odd number of valence electrons are known as free radicals due to unpaired electrons.

Expanded Octet: Atoms of the third period and beyond may be surrounded by more than 4 pairs of electrons in certain compounds that have orbitals with an energy low enough to accommodate extra electrons.

Metallic Bonds in Detail

Metallic Bond: Characterized by having few valence electrons, which cannot form covalent bonds. By sharing their electrons, they cannot achieve a noble gas structure.

Characteristics of Metals:

  • Exhibit shine (luster).
  • Are ductile and malleable.
  • Emit electrons.
  • Are poorly soluble in solvents.

Classification of Metal Links:

  • Conductors: Electrons tightly packed (e.g., Au, Cu, Pt).
  • Semiconductors: Electrons spaced 6 to 8.
  • Insulators: Separated electrons hardly appear.

Coordinate Covalent Bond: A bond that occurs when two atoms share a pair of electrons, but this pair is provided by only one of the combined atoms. Also called dative covalent bond.

Van der Waals Forces: Forces between bodies that are electrical dipoles, either instantaneous or permanent (e.g., F, Cl, Br, I).

Hydrogen Bonding: Occurs when hydrogen is bonded to a highly electronegative element, generating a permanent dipole.

Example: Alcohols, acids, ketones.

Glass, Ceramic, and Polymers

Structures and crystal properties are determined by the type of force that holds particles together.

Types of Glass:

  • Ionic: Electrostatic attraction, brittle, non-conductor.
  • Covalent: Covalent bonds, high melting point, poor conductor.
  • Molecular: Dispersion forces, soft, low melting point, poor thermal and electrical conductor.
  • Metallic: Hard link, soft metal, melting point high or low, good conductor.

Examples: Birth, Cf, CaCO3, MgO.

Polymers: From the Greek poly (many) and meros (parts), a substance whose molecule can be multiples of its molecular weight.

Natural Polymers: Fibers composed of cellulose found in wood are used to make candles and paper.

Ceramics: Substances made from feedstock that is burnt clay, such as lead, water, etc.

Uses: Hollow bricks, bricks, and porcelain tiles.

Lattice Energy and Related Concepts

Lattice Energy: Energy required to completely separate one mole of a solid ionic compound into its gaseous ions.

Coulomb’s Law: The potential energy between two ions is directly proportional to the product of their charges and inversely proportional to the distance that separates them.

Born-Haber Cycle: This procedure relates the lattice energy of ionic compounds with ionization energies, electron affinity, and other properties.

Sublimation: Solid lithium converting to steam.

Hybridization: Used to explain the mixture of atomic orbitals to generate a set of hybrid orbitals. Hybridization occurs when an atom’s orbitals are mixed.

Molecular Geometry

Molecular Geometry: Refers to the three-dimensional arrangement of atoms in a molecule, which affects their physical and chemical properties.