Lecture on Chemical Bonds: Crash Course Chemistry

Introduction

• Humans and chemicals are analogous in that both are about bonds.
• Various types of human relationships have different requirements.
• Distance is crucial as it affects focus and space in relationships.
• Atoms form bonds similar to human relationships to reduce stress and energy.

Why Atoms Bond

• Atoms bond to lower their overall energy by balancing attractive and repulsive forces.
• Electrostatic force plays a key role: electrons are attracted to protons of another atom.
• Like charges repel, opposite charges attract.

Bond Length and Energy

• Atoms achieve a balance at a specific distance known as bond length.
• Bond length results when attractive and repulsive forces cancel each other out.
• Example: Chlorine bond length and energy (Cl₂) is 0.00199 nm and -239 kJ/mol.

Covalent Bonds

• Electrons are shared between atoms in covalent bonds.
• Electronegativity affects electron sharing:
  • Higher electronegativity attracts electrons more.
  • Creates polar covalent bonds when electrons are unevenly distributed (e.g., water H₂O).
  • Non-polar covalent bonds occur when electrons are evenly distributed.

Ionic Bonds

• Formed between positive ions (metals) and negative ions (non-metals) through electron transfer.
• Example: Sodium chloride (NaCl); bond energy calculated using Coulomb’s Law:
  • Energy = Product of charges / Distance (\times) Constant
  • Shows strong attraction between oppositely charged ions.

Types of Bonds

1. Non-polar Covalent Bonds:
   • Equal sharing of electrons between non-metals or metalloids.
2. Polar Covalent Bonds:
   • Uneven sharing due to different electronegativities.
3. Ionic Bonds:
   • Transfer of electrons from a metal to a non-metal.

• Bonds exist on a continuum, similar to human relationships.

Properties of Bond Types

• Ionic Compounds:
  • Often form crystalline solids.
  • Soluble in water and conduct electricity when dissolved.
• Covalent Compounds:
  • Can be gases, liquids, or softer solids.
  • Generally not water-soluble and do not conduct electricity.
• Polarity plays a critical role in determining these properties.

Conclusion

• Bonds form to minimize energy between atoms or ions.
• Covalent bonds involve electron sharing; ionic bonds involve electron transfer.
• Use Coulomb’s law to calculate ionic bond energy.

Acknowledgments

• Written by Edi González, edited by Blake de Pastino.
• Chemistry consultant: Dr. Heiko Langner.
• Directed by Nicholas Jenkins.
• Graphics by Thought Café.