Chemical Bonding Basics

Chemical bonds are the forces that hold atoms together in molecules or compounds, arising from the interactions of electrons. These bonds determine the structure, stability, and reactivity of substances. From the salt in your kitchen (\( \ce{NaCl} \)) to the water you drink (\( \ce{H2O} \)), bonding governs chemistry. This article covers bond types, their properties, Lewis structures, and practical examples.

Types of Chemical Bonds

The main types of chemical bonds are:

  • Ionic Bonds: Formed by electron transfer between a metal and non-metal, creating oppositely charged ions. Example: \( \ce{Na + Cl -> NaCl} \), where \( \ce{Na+} \) and \( \ce{Cl-} \) are held by electrostatic attraction.
  • Covalent Bonds: Formed by electron sharing between non-metals. Example: \( \ce{H2} \) shares one pair: \( \ce{H:H} \). Can be single, double (\( \ce{O2} \)), or triple (\( \ce{N2} \)).
  • Metallic Bonds: Electrons delocalized among metal atoms, e.g., in copper (\( \ce{Cu} \)), explaining conductivity.

Polar covalent bonds (e.g., \( \ce{H2O} \)) involve unequal sharing due to electronegativity differences.

Bond Properties

Bonds vary in strength and length:

  • Bond Energy: Energy to break a bond. \( \ce{H-H} \): 436 kJ/mol; \( \ce{O=O} \): 498 kJ/mol (double bond, stronger).
  • Bond Length: Distance between nuclei. \( \ce{H-H} \): 74 pm; \( \ce{C-C} \): 154 pm (single); \( \ce{C=C} \): 134 pm (double, shorter).

Ionic bonds form lattices (high melting points), while covalent bonds form discrete molecules or networks (e.g., diamond).

Lewis Structures

Lewis structures represent bonding with dots for valence electrons:

Steps:

  1. Count total valence electrons.
  2. Arrange atoms, connect with single bonds.
  3. Distribute remaining electrons to satisfy octets.

Example: \( \ce{CO2} \):

  • C: 4, O: 6 × 2 = 16 electrons total.
  • Structure: \( \ce{O=C=O} \) (double bonds).
\[ \ce{:O::C::O:} \]

Exceptions: \( \ce{BF3} \) (B has 6 electrons).

Applications

Bonding impacts everyday life:

  • Materials: Ionic \( \ce{NaCl} \) in salt; covalent \( \ce{SiO2} \) in glass.
  • Biology: Covalent peptide bonds in proteins.
  • Technology: Metallic bonds in wires; covalent polymers in plastics.

Bond knowledge drives drug design, nanotechnology, and more.